Fluidic propulsive system and thrust and lift generator for aerial vehicles

ABSTRACT

A vehicle includes a main body and a gas generator producing a gas stream. At least one fore conduit and tail conduit are fluidly coupled to the generator. First and second fore ejectors are fluidly coupled to the at least one fore conduit. At least one tail ejector is fluidly coupled to the at least one tail conduit. The fore ejectors respectively include an outlet structure out of which gas from the at least one fore conduit flows. The at least one tail ejector includes an outlet structure out of which gas from the at least one tail conduit flows. First and second primary airfoil elements have leading edges respectively located directly downstream of the first and second fore ejectors. At least one secondary airfoil element has a leading edge located directly downstream of the outlet structure of the at least one tail ejector.

PRIORITY CLAIM

This application is a divisional of U.S. patent application Ser. No.15/256,178, which claims priority to U.S. Provisional Application No.62/213,465, filed Sep. 2, 2015, the entire disclosures of each of whichare hereby incorporated by reference as if fully set forth herein.

COPYRIGHT NOTICE

This disclosure is protected under United States and InternationalCopyright Laws. ©2018 Jetoptera. All rights reserved. A portion of thedisclosure of this patent document contains material which is subject tocopyright protection. The copyright owner has no objection to thefacsimile reproduction by anyone of the patent document or the patentdisclosure, as it appears in the Patent and Trademark Office patent fileor records, but otherwise reserves all copyrights whatsoever.

BACKGROUND

Aircraft that can hover, take off and land vertically are commonlyreferred to as Vertical Take-Off and Landing (VTOL) aircraft. Thisclassification includes fixed-wing aircraft as well as helicopters andaircraft with tilt-able powered rotors. Some VTOL aircraft can operatein other modes as well, such as Short Take-Off and Landing (STOL). VTOLis a subset of V/STOL (Vertical and/or Short Take-off and Landing).

For illustrative purposes, an example of a current aircraft that hasVTOL capability is the F-35 Lightning. Conventional methods of vectoringthe vertical lift airflow includes the use of nozzles that can beswiveled in a single direction along with the use of two sets of flatflapper vanes arranged 90 degrees to each other and located at theexternal nozzle. The propulsion system of the F-35 Lightning, similarly,provides vertical lifting force using a combination of vectored thrustfrom the turbine engine and a vertically oriented lift fan. The lift fanis located behind the cockpit in a bay with upper and lower clamshelldoors. The engine exhausts through a three-bearing swivel nozzle thatcan deflect the thrust from horizontal to just forward of vertical. Rollcontrol ducts extend out in each wing and are supplied with their thrustwith air from the engine fan. Pitch control is affected via liftfan/engine thrust split. Yaw control is through yaw motion of the engineswivel nozzle. Roll control is provided by differentially opening andclosing the apertures at the ends of the two roll control ducts. Thelift fan has a telescoping “D”-shaped nozzle to provide thrustdeflection in the forward and aft directions. The D-nozzle has fixedvanes at the exit aperture.

The design of an aircraft or drone more generally consists of itspropulsive elements and the airframe into which those elements areintegrated. Conventionally, the propulsive device in aircraft can be aturbojet, turbofan, turboprop or turboshaft, piston engine, or anelectric motor equipped with a propeller. The propulsive system(propulsor) in small unmanned aerial vehicles (UAVs) is conventionally apiston engine or an electric motor which provides power via a shaft toone or several propellers. The propulsor for a larger aircraft, whethermanned or unmanned, is traditionally a jet engine or a turboprop. Thepropulsor is generally attached to the fuselage or the body or the wingsof the aircraft via pylons or struts capable of transmitting the forceto the aircraft and sustaining the loads. The emerging mixed jet (jetefflux) of air and gases is what propels the aircraft in the oppositedirection to the flow of the jet efflux.

Conventionally, the air stream efflux of a large propeller is not usedfor lift purposes in level flight and a significant amount of kineticenergy is hence not utilized to the benefit of the aircraft, unless itis swiveled as in some of the applications existing today (namely theBell Boeing V-22 Osprey). Rather, the lift on most existing aircraft iscreated by the wings and tail. Moreover, even in those particular VTOLapplications (e.g., take-off through the transition to level flight)found in the Osprey, the lift caused by the propeller itself is minimalduring level flight, and most of the lift force is nonetheless from thewings.

The current state of art for creating lift on an aircraft is to generatea high-speed airflow over the wing and wing elements, which aregenerally airfoils. Airfoils are characterized by a chord line extendedmainly in the axial direction, from a leading edge to a trailing edge ofthe airfoil. Based on the angle of attack formed between the incidentairflow and the chord line, and according to the principles of airfoillift generation, lower pressure air is flowing over the suction (upper)side and conversely, by Bernoulli law, moving at higher speeds than thelower side (pressure side). The lower the airspeed of the aircraft, thelower the lift force, and higher surface area of the wing or higherangles of incidence are required, including for take-off.

Large UAVs make no exception to this rule. Lift is generated bydesigning a wing airfoil with the appropriate angle of attack, chord,wingspan, and camber line. Flaps, slots and many other devices are otherconventional tools used to maximize the lift via an increase of liftcoefficient and surface area of the wing, but it will be generating thelift corresponding to at the air-speed of the aircraft. (Increasing thearea (S) and lift coefficient (C_(L) allow a similar amount of lift tobe generated at a lower aircraft airspeed (V0) according to the formulaL=½ ρV²SC_(L), but at the cost of higher drag and weight.) These currenttechniques also perform poorly with a significant drop in efficiencyunder conditions with high cross winds.

While smaller UAVs arguably use the thrust generated by propellers tolift the vehicle, the current technology strictly relies on control ofthe electric motor speeds, and the smaller UAV may or may not have thecapability to swivel the motors to generate thrust and lift, ortransition to a level flight by tilting the propellers. Furthermore, thesmaller UAVs using these propulsion elements suffer from inefficienciesrelated to batteries, power density, and large propellers, which may beefficient in hovering but inefficient in level flight and createdifficulties and danger when operating due to the fast moving tip of theblades. Most current quadcopters and other electrically powered aerialvehicles are only capable of very short periods of flight and cannotefficiently lift or carry large payloads, as the weight of the electricmotor system and battery may already be well exceeding 70% of the weightof the vehicle at all times of the flight. A similar vehicle using jetfuel or any other hydrocarbon fuel typically used in transportation willcarry more usable fuel by at least one order of magnitude. This can beexplained by the much higher energy density of the hydrocarbon fuelcompared to battery systems (by at least one order of magnitude), aswell as the lower weight to total vehicle weight ratio of a hydrocarbonfuel based system.

Accordingly, there is a need for enhanced efficiency, improvedcapabilities, and other technological advancements in aircraft,particularly to UAVs and certain manned aerial vehicles.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIGS. 1A-1C illustrate some of the differences in structure, forces, andcontrols between a conventional electric quadcopter and one embodimentof the present invention.

FIG. 2A is a top view of a conventional wing and airplane structure;FIG. 2B is a front view of a conventional wing and airplane structure.

FIG. 3 is a cross-section of one embodiment of the present inventiondepicting only the upper half of an ejector and shows profiles ofvelocity and temperature within the internal flow.

FIG. 4 is an embodiment of the present invention depicting apropulsor/ejector placed in front of an airfoil.

FIG. 5 is another embodiment of the present invention where thepropulsor/ejector is placed in front of a control surface as part ofanother wing airfoil.

FIGS. 6A-6C illustrates the present invention shown in FIG. 5 fromdifferent points of view.

FIG. 7A is another embodiment of the present invention that utilizes ajet efflux and airfoil in its wake to push the aircraft forward andgenerates lift, replacing the engine on the wing.

FIG. 7B is the front view of the present invention shown in FIG. 7A.

FIG. 7C is another embodiment of the present invention that featurestandem wings.

FIG. 8A is a side view of another embodiment of the present invention,featuring the tandem thrust/lift generation system where the frontthrust augmenting ejectors are producing thrust with a canard wing andthe rear thrust augmenting ejectors are producing thrust and lift in theaft region.

FIG. 8B is the perspective view of the present invention shown in FIG.8A.

FIG. 9 is a perspective view of the present invention shown in FIGS. 8Aand 8B and features the aircraft tail arrangements and the gas generatormount.

FIGS. 10A-10E show lift coefficient variations at a constant airspeed ofan airfoil as function of the angle of incidence showing stalling angleof attack.

FIGS. 11A-11B show stall margin improvement with different placements ofthe present invention.

FIGS. 12A-12C is yet another embodiment of the present invention thatfeatures the ejector component of the propulsor in relative position tothe wing.

FIGS. 13A-13C illustrates how the present invention can control theaircraft's pitch, roll and yaw using the thrust augmenting ejectors inconjunction with the thin airfoils placed in the ejectors' wake.

FIG. 14 is one embodiment of the present invention with flap-likeelements to the diffusor walls of a Coanda ejector which is itself splitin 2 halves.

FIGS. 15A-15C illustrates the 3D features, one embodiment invention,from different points of view.

FIG. 16A shows another embodiment of the present invention to improveperformance and margin of stall.

FIGS. 16B-16D illustrates the present invention shown in FIG. 16A fromdifferent points of view.

FIG. 17A-17C illustrate yet another embodiment of the present invention.

FIGS. 18A-18D show typical conventional arrangements for Coanda-typeejectors.

FIG. 18E is one embodiment of the present invention depicting circularCoanda ejector with simple primary nozzle elements.

FIG. 19A-19D depict different embodiments of the present inventionfeaturing primary nozzles with better performance.

FIG. 19E illustrates the flow over the delta wing obstruction placedinside the primary nozzle in its center.

FIG. 20 explains the thermodynamics of an embodiment of the presentinvention.

FIG. 21 is yet another embodiment of the present invention and featuresfor improving flow separation delay.

FIG. 22A through 22F illustrate different 3D features and embodiments ofthe present invention.

FIG. 23 illustrates certain features according to an embodiment of thepresent invention.

FIG. 24 demonstrates a Coanda-type ejector as applied to an aircraft forVTOL only.

FIG. 25 shows an alternative arrangement of the ejector as anotherembodiment of the present invention.

FIG. 26A shows a high-bypass turbofan.

FIG. 26B shows a modified turbofan to serve as gas generator as oneembodiment of the present invention.

FIG. 27A is one embodiment of the present invention featuring the bleedand conduits network.

FIG. 27B is another embodiment of a bleed and conduits network.

FIG. 27C is yet another embodiment of a bleed and conduits networkshowing the controller and sensors.

FIG. 27D is still another embodiment of a bleed and conduits networkshowing the controller and identified sensors.

FIGS. 28A-28E are possible shapes of propulsors of the presentinvention.

FIG. 29 is a possible arrangement of propulsion system at take-off orhovering in one embodiment of the present invention.

FIG. 30A-30B illustrate the thermodynamic cycles of a jet engine.

FIG. 31A-31B are one embodiment of the present invention.

DETAILED DESCRIPTION

This application is intended to describe one or more embodiments of thepresent invention. It is to be understood that the use of absoluteterms, such as “must,” “will,” and the like, as well as specificquantities, is to be construed as being applicable to one or more ofsuch embodiments, but not necessarily to all such embodiments. As such,embodiments of the invention may omit, or include a modification of, oneor more features or functionalities described in the context of suchabsolute terms. In addition, the headings in this application are forreference purposes only and shall not in any way affect the meaning orinterpretation of the present invention.

The present inventions disclosed in this application, eitherindependently and working together, allow a UAV to perform the maneuversof an electric UAV without the use of large propellers or fans whilealso maximizing the vehicle's autonomy, range, and payload to totalweight ratio. The electric UAVs such as a quadcopter can hover, take-offvertically and land as such, execute loops etc. by simply controllingthe rotation speed of the propellers attached to it. The presentinvention eliminates the need of propellers or large fans and replacesthe control logic of the rotational speed of the propellers with mainlyfluidic control of swiveling thrust augmenting ejectors supplied with amotive fluid from a gas generator on board of the vehicle. Non-electricUAVs employing jet engines typically do not operate at low speeds orefficiently and are limited in their maneuverability when compared toelectric UAVs. FIGS. 1A through 1C illustrate some of the differences instructure, forces, and rotation speeds between a conventional electricquadcopter and a fluidic quadcopter, one of embodiments of the presentinvention.

The present invention introduces several elements that increasesignificantly the maneuverability of a non-electric UAV. For example,one embodiment of the present invention discloses a novel propulsiondevice (propulsor) that can be deployed on an aircraft. Anotherembodiment describes the novel 3D elements implemented in ejectors aspart of the propulsor. Yet another embodiment discloses a tandem systemcombining a thrust generator (propulsor) and a thin airfoil wing(lifting element) that can both be deployed on an aircraft. Stillanother embodiment describes a particular tandem system that consists ofan ejector nozzle and a thin airfoil placed in the nozzle's wake anduses the jet efflux from the nozzle for thrust and lift generation.Another embodiment discloses novel placement of an ejector over a wingto allow for a high angle of incidence flight. One more embodimentdiscloses the application of a thermodynamic cycle of the propulsionsystem with optionally advantageous features that increase theefficiency and reduce the overall weight of the propulsion system.Finally, another embodiment describes a thrust generating system thatcombines VTOL capabilities with turbo machinery and control of pitch,roll, and yaw of an aerial vehicle. Each of the aforementionedembodiments and many more embodiments of the present inventionsdisclosed in this application will be further explained in the followingsections.

Propulsion Device and Thrust System.

FIGS. 2A and 2B describe a conventional aircraft with wing mountedengines that produce thrust, which generate acceleration and speed ofthe aircraft, resulting in generation of lift on the wings; the functionof the engine is to create the thrust and the jet efflux from the engineis not used for further generation of lift, but it is lost to ambient.The jet efflux has a velocity higher than that of the aircraft, and assuch, the lift generated by the wing is a function of the airspeed ofthe aircraft and not the local engine jet efflux speed, which is theobject of the current application.

One embodiment of the present invention includes a propulsor thatutilizes fluidics for the entrainment and acceleration of ambient airand delivers a high speed jet efflux of a mixture of the high pressuregas (supplied to the propulsor from a gas generator) and entrainedambient air in an engineered manner directly towards an airfoil placedexactly behind the propulsor, in the wake of the propulsor jet, and in asymmetrical or non-symmetrical manner.

FIG. 3 illustrates a cross-section of only the upper half of ejector200. Plenum 211 is supplied with hotter than ambient air. Pressurizedmotive gas stream 600 communicates via conduits with primary nozzles 203to the inner side of the ejector. The primary nozzles accelerate themotive fluid 600 to the speed required by the ejector performance, perdesign of the primary nozzles 203. The primary (motive) fluid 600emerges at high speed over the Coanda surface 204 as a wall jet,entraining ambient air 1 which may be at rest or approaching the ejectorat non-zero speed from the left of the figure. The mix of the stream 600and the ambient 1 are moving purely axially at the throat section 225 ofthe ejector. Through diffusion in the diffuser 210, the mixing andsmoothing out process continues so the profiles of temperature (750) andvelocity in the axial direction (700) have no longer high and low valuesas they do at the throat section 225, but become more uniform at theexit of the ejector. As the mixture of 1 and 600 approaches the exitplane, the temperature and velocity profiles are almost uniform; inparticular, the temperature of the mixture is low enough to be directedtowards an airfoil such as a wing or control surface.

In FIG. 4, another embodiment of the present invention is illustrated,with the propulsor/ejector 200 placed in front of an airfoil 100 andgenerating a lift force 400. The local flow over airfoil 100 is athigher speed than the speed of the aircraft, due to higher velocity 300of propulsor 200 exit jet efflux in comparison with aircraft air-speed500. The propulsor mixes vigorously a hotter motive stream provided bythe gas generator with the incoming cold ambient stream of air at highentrainment rate. The mixture is homogeneous enough to reduce the hotmotive stream 600 of the ejector temperature to a mixture temperatureprofile 700 that will not impact the airfoils 100 or 150 mechanically orstructurally. The velocity profile of the efflux jet leaving thepropulsor 200 is such that it will allow more lift 400 to be generatedby airfoil 100 due to higher local speeds. Additional control surfacescan be implemented on the airfoil 100, such as elevator surface 150shown here. By changing the angle of such surfaces 150, the attitude ofthe aircraft can rapidly be changed with little effort given the higherlocal velocity of the jet efflux, 300.

FIG. 5 illustrates that the propulsor/ejector 200 may also be placed infront of a control surface 152 as part of another wing airfoil 101. Thepropulsor may be a non-axisymmetric shape, and the control surface maybe placed exactly in the wake of said propulsor 200. The propulsor mixesvigorously a hotter motive stream provided by the gas generator, withthe incoming cold ambient stream of air at high entrainment rate.Similarly, the mixture is homogeneous enough to reduce the hot motivestream 600 of the ejector temperature to a mixture temperature profilethat will not impact the control surface mechanically or structurally.In this embodiment, yaw can be controlled by changing the orientation ofcontrol surface 152. The propulsor 200 main function is to generatethrust but also lift or attitude control. In this embodiment, yawcontrol is in direction 151 creating a rotation around the aircraft axis10.

FIGS. 6A through 6C show the illustration in FIG. 5 from differentpoints of view.

For example, an emerging jet having a rectangular pattern due to therectangular exhaust plane of the propulsor can also be vectored mucheasier and in more directions than a propeller and electric motor. Inanother example, an emerging jet having a rectangular pattern due to therectangular exhaust plane of the propulsor is directed towards theleading edge of a short wing placed at certain distance behind thepropulsor to maximize the lift benefit. As described in the presentinvention, the propulsor can therefore generate the thrust necessary forthe aircraft to travel forward, in the direction mostly opposite to thedirection of the jet efflux. In addition, the jet efflux moving athigher speed than the aircraft's speed and resulting from said propulsoror ejector will be used to augment the lift force that results from itsflow over the airfoil placed behind said propulsor or ejector. Thevelocity of the jet will always need to exceed the velocity of theaircraft and the difference between the two velocities will need to beminimal in order to maximize the propulsive efficiency. It follows thatthe higher the mass of flow providing the thrust at lower speeds, yethigher than the aircraft speed, the higher the propulsive efficiency.For example, using a propulsive efficiency equation known by thosefamiliar with the art:PE=2V0/(V+V0)

where V is the propulsor exit jet velocity and V0 is the airspeed of theaircraft, if the propulsion jet velocity is 150% of the aircraftairspeed, the airspeed of the aircraft will be 50% of that of theemerging jet velocity of the propulsor, and the propulsive efficiencywill be 80%. After leaving the exhaust section of the propulsor of aplane, the exhaust stream of most conventional jet airplanes is lost tothe environment and no benefit is drawn from the residual jet, althoughthe jet from e.g. a jet engine still carries energy in the wake. Theexhaust flow is typically a round jet at higher speeds (and thereforeenergy), mixing with a parallel flow at lower speed and eventuallymixing with the aircraft trailing vortex pair. Once it leaves the planeengine as exhaust, the jet efflux no longer benefits the aircraft andthe higher the velocity of the exhaust jet, the lower the propulsiveefficiency and the waste of energy to the ambient.

One embodiment of the present invention utilizes the mixed stream thatemerges from the present invention propulsor, which otherwise would belost to ambient in conventional aircraft, to generate lift or createdirection-changing capabilities by directing it straight to a thinairfoil wing or other surface placed directly behind the said propulsor,for lift generation or aircraft attitude changes. Since the supply ofpressurized gas can be further modulated or used in a segmented way viaa network contained by the aircraft fuselage and wings, the entrainmentand velocity of the efflux jet can be dialed via primary or secondarymethods. The primary method refers to the modulation of pressure, flow,temperature, and/or segmentation (multiple supplies to multiplepropulsors distributed across the aircraft). The concept of segmentationinvolves the use of multiple propulsor elements conveniently placedthroughout an aircraft, i.e. segmenting the function of a single, largepropulsor into multiple smaller ones that are being supplied with thepressurized gas via a network of conduits. A secondary method mayinvolve changing geometry or position of the propulsor with respect tothe neutral position of that propulsor. For example, in level flight,supplying the appropriate gas pressure and flow to the propulsor mayresult in a jet efflux at 125% of the airspeed of the aircraft. In thecase of a 125% jet efflux axial velocity that is greater than theaircraft airspeed, the propulsive efficiency becomes 88%. If theemerging velocity becomes 110% at higher speeds with same thrust levelgenerated via entrainment of ambient air, then the propulsive efficiencyimproves to 95%.

Thrust and Lift Generator

Another embodiment of the present invention relates generally to acombination of thrust and lift obtained via a tandem system composed ofa thrust generation element which directs a high speed, non-circularefflux jet with mostly axial direction velocity component over a thinairfoil located downstream of the efflux jet. The local high axialvelocity of this efflux jet generates lift at considerably higher levelsthan the lift of the aircraft speed regular wing as ˜(Jet streamVelocity)². The efflux jet is a mixture of hot, high energy gases,provided to the thrust generator via conduits from a high pressure gasgenerator outlet, and entrained surrounding air. The entrained air isbrought to high kinetic energy level flow via a momentum transfer by thehigh pressure gases supplied to the thrust generator inside the thrustgenerating element. The resulting mixture of air and gas emerges out ofthe thrust generator and can be directed to point mainly in the axial,down-stream direction, towards a thin airfoil leading edge and/or thepressure side of the airfoil.

In most conventional aircraft, it is not currently possible to directthe jet efflux at an airfoil or wingfoil to utilize its lost energy. Inthe case of turbojets, the high temperature of the jet efflux actuallyprecludes its use for lift generation via an airfoil. Typical jetexhaust temperatures are 1000 degrees Centigrade and sometimes higherwhen post-combustion is utilized for thrust augmentation, as is true formost military aircraft. When turbofans are used, in spite of the usageof high by-pass on modern aircraft, a significant non-axial directionresidual element still exists, due to the fan rotation, in spite ofvanes that direct the fan and core exhaust fluids mostly axially. Thepresence of the core hot gases at very high temperatures and theresidual rotational movement of the emerging mixture, in addition to thecylindrical nature of the jets in the downwash, make the use of airfoilsdirectly placed behind the turbofan engine impractical. In addition, themixing length of hot and cold streams from the jet engines such asturbofans is occurring in miles, not inches. On the other hand, thecurrent use of larger turboprops generate large downwash cylindricalairflows the size of the propeller diameters, with a higher degree ofrotational component velocities behind the propeller and moving largeamounts of air at lower speeds. The rotational component makes itdifficult to utilize the downstream kinetic energy for other purposesother than propulsion, and hence, part of the kinetic energy is lost andnot efficiently utilized. Some of the air moved by the large propellersis also directed to the core of the engine. In summary, the jet effluxfrom current propulsion systems has residual energy and potential notcurrently exploited.

In this embodiment of the present invention, the stream can be used as alift generation stream by directing it straight to a thin airfoil forlift generation. For example, where a jet efflux axial velocity that is125% greater than the aircraft airspeed, the portion of the wingreceiving the jet efflux stream can generate more than 50% higher liftfor the same wingspan compared to the case where the wingspan is washedby the airspeed of the aircraft air. Using this example, if the jetefflux velocity is increased to 150%, the lift becomes more than 45%higher than the original wing at aircraft airspeed, including a densitydrop effect if a pressurized exhaust gas from a turbine was used, forinstance.

Alternatively, a wing such as a light wingfoil could be deployeddirectly behind the propulsor's ejector exit plane, immediately afterthe vehicle has completed the take-off maneuvers and is transitioning tothe level flight, helping generate more lift for less power from theengine.

Alternatively, using this embodiment of the present invention, the wingneed not be as long in wingspan, and for the same cord, the wingspan canbe reduced by more than 40% to generate the same lift. In this liftequation known by those familiar with the art:L=½ρV ² SC _(L)

where S is the surface area of the wing, ρ is the density, V is thevelocity of the aircraft (wing), and C_(L), is the lift coefficient. AUAV with a wingspan of e.g., 10 ft. can reduce the wingspan to merely 6ft. provided the jet is oriented directly to the wing at all timesduring level flight, with a wing that is thin and has a chord, camberand C_(L), similar to the original wing. The detrimental impact oftemperature on the density is much smaller, if the mixing ratio (orentrainment ratio) is large, and hence the jet is only slightly higherin temperature.

FIG. 7A describes one alternative approach to having the jet engineplaced on the wing and independently producing thrust. In FIG. 7A, thejet engine is no longer producing a jet efflux pushing the aircraftforward, but instead, is used as a gas generator and is producing astream of motive air for powering a series of ejectors that are embeddedin the wing for forward propulsion. In this embodiment, the gasgenerator (not shown) is embedded into the fuselage of the aircraft, andthe green portion represents the inlet, the gas generator and theconduits leading to the red ejectors, which are flat and, similarly toflaps or ailerons, can be actuated to control the attitude of theaircraft in addition to providing the required thrust. FIG. 7A furtherdepicts another (secondary) wing that is placed in tandem with the first(main) wing containing the thrust augmentation ejectors, just behind thesaid ejectors. The secondary wing hence receives a much higher velocitythan the airspeed of the aircraft, and as such it creates a high liftforce as the latter is proportional to the airspeed squared. In thisembodiment of the present invention, the secondary wing will see amoderate higher temperature due to mixing of the motive fluid producedby the gas generator (also referred to as the primary fluid) and thesecondary fluid, which is ambient air, entrained by the motive fluid ata rate between 5-25 parts of secondary fluid per each primary fluidpart. As such, the temperature that the secondary wing sees is a littlehigher than the ambient temperature, but significantly lower than themotive fluid, allowing for the materials of the secondary wing tosupport and sustain the lift loads, according to the formula:T _(mix)=(T _(motive) +ER*T _(amb))/(1+ER)

where T_(mix), is the final fluid mixture temperature of the jet effluxemerging from the ejector, ER is the entrainment rate of parts ofambient air entrained per part of motive air, T_(motive) is the hottertemperature of the motive or primary fluid, and T_(amb) is theapproaching ambient air temperature.

FIG. 7B depicts the front view of the aircraft shown in FIG. 7A witharrows illustrating the additional lift force generated by the shorter,tandem wings and lack of engines on the wing.

FIG. 7C depicts another embodiment of the present invention featuringthe tandem wings. In this embodiment, the thrust augmenting ejectors 701that are part of the propulsor system are placed on the main wings(forward wings) 703 and connected via conduits and receive the motivefluid from a gas generator placed inside the fuselage. The ejectorgenerates the thrust and transmits the force mechanically to theaircraft. The efflux jet generates a constant stream of high velocitywhich is used by the secondary wing (grey wing) 702 for producingadditional lift. The combination of the two shorter wings produce morelift than that of a much larger wingspan wing lacking the ejector thrustaugmenters that rely on a jet engine attached to said larger wing toproduce thrust.

FIGS. 8A and 8B illustrate yet another embodiment of the presentinvention. As shown in FIGS. 8A and 8B, the tandem thrust/liftgeneration system is attached to an aerial vehicle 804, where the frontthrust augmenting ejectors 801, which include leading edges and inletportions for intake of upstream air, are producing thrust just behind acanard wing, with one each of such ejectors positioned on the starboardand port side of the vehicle. The canard wing is oriented at a highangle of incidence and close to stall when flying level, wherein thepresence of the thrust augmenting ejector extends the stall margin ofsaid canard wing 803. The thrust augmenting ejector 801 transmitsmechanically the force of thrust to the structure 804 and produces adownstream jet efflux consisting of well mixed primary and secondary airstreams, which in turn are used to generate significantly higher lift onwing 802. The system is replicated also on the tail of the aircraft in asimilar fashion. The thrust augmenting ejectors 801 receive a compressorbleed stream from gas generator 800, whereas the tail thrust augmentorejectors receive the pressurized, hot gases exiting the gas turbine ofthe gas generator 800. The combination of using compressor bleed air forthe 801 ejectors and using hot exhaust gas for the tail ejectors asprimary fluids, respectively, result in (1) thrust augmentation in levelflight due to the ejectors entrainment of ambient air and (2) additionallift generated on surfaces placed behind the said ejectors, such as wing802 having leading edges. These elements placed behind the ejector aregenerally thin structures, and could be constructed out of compositematerials, including but not limited to ceramic matrix composites(CMCs). This arrangement offers greater flexibility to switch duringtransition from take-off to hovering to level flight and landing.

FIG. 9 provides further details to the tail (or hot) section of theillustration in FIGS. 8A and 8B. The thin structures 904 having leadingedges are placed in the wake of a set of hot thrust augmenting ejectors901, which have leading edges and receive the primary (motive) fluid ashot exhaust gas from the gas generator 800, situated near a cockpit 805and entraining air in the inlet of element 901, namely 902. The conduitlinking the exhaust of the gas generator 800 to element 901 is embeddedinto the vertical fin structure 950. The ejectors 901 entrain theincoming ambient air in the inlet areas 902 and eject a high velocity,entrained air and motive gas mixture at outlet 903 and mainly towardsthe thin tail structure 904, which in turn generates additional lift.Both elements 801 in FIGS. 8A and 8B and 901 in FIG. 9 can swivel aroundtheir main axis for VTOL and hovering control. Additionally, eachejector of the ejector set 901 can rotate about the same axis withand/or independent of the other ejector.

FIGS. 10A through 10E show the various flows as well as the lift versusangle of incidence with the point corresponding to the angle ofincidence highlighted in each instance. As the angle of incidence of agiven airfoil is increased, the lift increases until separation of theboundary layer on the airfoil determines stall, right after the maximumlift point (see FIG. 10D).

FIG. 10A demonstrates the lift and angle of incidence of the canard wingstructure 203 illustrated in FIGS. 8A and 8B at a zero degree (0°) angleof incidence, where the dot represents the lift force and thestreamlines represent the flows around the canard airfoil. FIGS. 10Bthrough 10D show the result of increase of lift force of the structure203 as the angle of incidence or angle of attack increases to the stallpoint, fully represented at FIG. 10D. Beyond the position of the airfoil(with respect to the angle of incidence) as shown in FIG. 10D, e.g., atposition depicted in FIG. 10E, the lift decreases rapidly as the flowbecomes turbulent, may separate and streamlines no longer are smooth.The lift increases almost linearly as the angle of incidence isincreased, but at the angle of incidence shown in FIG. 10D it reachesthe maximum value, beyond which the flow separates on the upper side ofthe airfoil. In FIG. 10E, there is recirculation and increased drag,loss of lift generated by opposite flows, and occurrence of theseparation of boundary layers. This causes the lift force to dropsignificantly and result in stall.

FIGS. 11A and 11B show the characteristic lift curve of FIGS. 10Athrough 10E, with a second curve showing an extension of the stallmargin, which demonstrates the improvement in the lift versus angle ofincidence beyond the stall point in case the ejector is placed relativeto the wing such that it delays separation and facilitates ingestion ofthe boundary layer at high angles of attack. In FIG. 11B, the liftcontinues to increase without stall with the angle of incidence, due tothe presence of the ejector. The placement of the ejector beyond theapex of the airfoil allows re-attachment or separation avoidance of theflow of the upper boundary layer which otherwise would separate in theabsence of the ejector that ingests the said boundary layer, due to ahigh angle of incidence of said airfoil. The ejector is introducing alow pressure local area at its inlet, forcing the ingestion of theboundary layer developed over the upper side of the wing airfoil. Themargin of the stall becomes much larger by placing the thrust augmenterejector beyond the apex of the canard wing or airfoil 203 of FIGS. 7C,8A, and 8B. These results indicate that the presence of the ejectorextends the stall margin and allows for greater lift forces to begenerated by increasing the angle of attack beyond the stall angle ofattack value of said airfoil without the presence of the ejector. Inaddition, FIGS. 11A and 11B illustrates possible placements of theejector with respect to the airfoil chord to re-streamline the flowaround the airfoil.

FIGS. 12A through 12C depict yet another embodiment of the presentinvention. The main wing and thrust augmenting ejector system produces aforward thrust and a high velocity jet efflux conditioning that can beused for additional lift generation when coupled with a secondaryairfoil (not shown, but could be placed in the wake or efflux downstreamof the ejectors). As illustrated in FIG. 12A, the ejectors are formed bytwo (2) airknife-like halves, which together generate the entrainment,momentum transfer, and acceleration of the ambient air by using theprimary or motive fluid and ejecting the final mixture of primary andsecondary fluids at high speeds. The two halves 1201 and 1202 canindependently rotate and translate to position themselves and relativeto the wing in such manner that they are optimizing the augmentation atany time, based on the aircraft attitude and mission (or point inmission), primary fluid condition (flow rate, pressure and temperature).This allows the throat formed by the two halves to have, in oneinstance, a certain value, yet in another instance, a larger or smallervalue. For example, at take-off, the two halves may both point downwardsto enable the aircraft to vertically take-off. The two halves may moveindependently and in position to one another to maximize thrust with amaximum primary fluid flow rate and maximum entrainment rate, generatinga certain area inlet ratio to the throat that is favorable to maximizingthe thrust. Yet when flying level, the two ejector halves may instead beboth horizontal and streamlined with the wing, with a smaller throatarea for smaller pressures, temperature and flow rate of the primaryfluid, again maximizing the thrust augmentation. The throat area, theexit area, the inlet area, and their ratios may also be adjustedaccording to a maximization of thrust algorithm. Both 1201 and 1202contain a plenum 1211 and 1212 respectively, connected to a conduit andreceiving the said primary fluid from, e.g., a compressor bleed port ofa gas generator. The two halves form together a variable inlet area 1201a and a variable exit area 1201 b and a diffusing shape formed by walls1213 and 1214 respectively, to optimally diffuse the flow to maximizesaid thrust. The primary flow is introduced from the plenums 1211 and1212 respectively into the throat area via multiple specially designednozzles 1203 and 1204 respectively, in a continuous or pulsed manner.

FIG. 12C further describes the arrangement of this ejector for levelflight of an aircraft. FIG. 12C shows that the flat ejector may beinserted within the thickness of the wing airfoil when all the elementsdescribed in this disclosure are used for highest efficiency. FIG. 12Cshows the contour of the said inner and outer ejector surfaces and FIG.12B shows the 3D model of the 1201 and 1202 lower and upper halves ofthe flat Coanda ejector disclosed, integrated with the wing. The twohalves, which can be independently actuated, form together an inlet 1201a and an outlet 1201 b; they allow high speed introduction of a primaryfluid through primary nozzles 1203 over Coanda surfaces 1204.

FIGS. 13A through 13C depict how the present invention can control theaircraft's pitch, roll and yaw using the thrust augmenting ejectors inconjunction with the thin airfoils placed in the ejectors' wake. Withregards to the pitch, the cold and hot ejectors may be independentlyrotated around their main axis to cause the aircraft to pitch forward oraft. Pitch control is affected via forward/aft ejector thrust splitand/or modulation of the flow of the motive fluid supplied to theejectors. With regards to the roll, the ejectors may be independentlyrotated to cause the aircraft to roll. With regards to the yaw, acombination of additional rotation around a perpendicular axis with thepositioning of the thin airfoils in the wake of the jet efflux may beused to cause a change in aircraft attitude. This embodiment of thepresent invention makes these maneuvers possible with the use of specialjoints that can swivel, transmit loads, and allow the passage of theprimary fluid to the said ejectors.

Coanda Device

In yet another embodiment of the present invention, the propulsor and/orthe thrust generator of the tandem system have the ability to entrainlarge amounts of air and accelerate it to the jet efflux speed. This isachieved by the employment of a Coanda device. These flow augmentationdevices have been generally described by different publications thatwill be discussed in greater detail below. For example, in his paper“Theoretical Remarks on Thrust Augmentation”, (Reissner AnniversaryVolume, Contributions to Applied Mechanics, 1949, pp 461-468), vonKarman describes in great detail why a Coanda device results insignificant higher thrust augmentation via multiple jets. Similarly,U.S. Pat. No. 3,795,367 (Mocarski) discloses a device for airentrainment with high augmentation ratios exceeding 1.8, while U.S. Pat.No. 4,448,354 (Reznick) applies a linear Coanda device to the VTOLcapability of a jet engine. In these aforementioned publications andother references not mentioned here, the application of Coanda deviceshas been limited and described only for VTOL and not for level flight.One major teaching was that the scalability and application forhorizontal flight was not practical, particularly for the axisymmetricdevices of Coanda type where their size would induce drag increase forlarger aircraft. An application for a small UAV however may be moresuitable with a higher degree of integration. Embodiments of the presentinvention are able to integrate the ejectors with the fuselage and theengine or propulsion system because the vehicle does not need toconsider large seat capacity. Integration as disclosed in theseembodiments is not currently practical or commercially reasonable inlarge commercial flights.

This embodiment of the present invention improves the Coanda device andapplies it using new techniques for better entrainment and delay oravoidance of separation in its aggressive turns inside the device. Whilethe compactness of these devices is critical for their deployment inaviation and other fields, the inlet part needs to be large in order toenhance the air entrainment. Reznick argues that a circular element ismore efficient than a linear one. Mocarski shows that entrainment iscritical to thrust augmentation. The diffusor part needs to be longenough to ensure no separation of the boundary layer occurs inside thedevice and mixing is complete at the exit of the device. Conventionally,these diffusers have been long with a very mild slope in order tominimize boundary separation risks.

The present invention shows improved entrainment in the devices by meansof novel elements that rely on 3D geometrical and fluid flow effects andutilization of separation avoidance techniques in the Coanda device. Thepreferred embodiment of the present invention has an entrainment ratiobetween 3-15, preferably higher. In another embodiment of the presentinvention, the device will receive the motive gas from a pressurizedsource such as a gas generator, a piston engine (for pulsed operations)or a compressor or supercharger. Another feature of the presentinvention is the ability to change the shape of the diffusor walls ofthe flat ejector utilized for propulsion by retracting and extending thesurfaces to modify the geometry such that maximum performance isobtained at all points of the aircraft mission. In addition, the need toswivel the entire ejector by 90 degrees for VTOL and hovering is nolonger needed, when the fully deployed diffusor walls are used to directthe jet efflux downward.

Another embodiment of the present invention introduces flap-likeelements to the diffusor walls of a Coanda ejector which is itself splitin 2 halves, illustrated in FIG. 14, as upper 1401 and lower 201 halfejectors that are each similar to an airknife. Elements 115 and 215 areactuators or linkages, enabling the movement of said surfaces to thedesired position on both 110 a and 210 a, respectively.

Yet another embodiment of the present invention discloses how staging 3Dinlet geometries and/or primary fluid slot 3D features, eitherindependently or working together, significantly improve the performanceof the propulsor, together with introduction of flow separationavoidance patterns on the propulsor. For example, as illustrated inFIGS. 15A through 15C, the 2D inlet is replaced by a 3D inlet. FIGS. 15Athrough 15C further illustrate the multiple 3D elements of the ejectordisclosed, improving its performance over baseline, and 2D ejectorshaving the inlet, throat and diffuser in the same planes, respectively.

The inlet may further match the boundary layer profile shape formedbehind the apex of a main wing airfoil of an aircraft (as illustrated inFIG. 16A), hence helping to ingest the boundary layer and delay theoverall stall (improving across all margins), further illustrated inFIG. 25 for the position with respect to the airfoil. FIGS. 11A and 11Billustrate the benefits of placing it as such, relative to the airfoiland its boundary layer profile.

FIG. 16A shows a one embodiment of the flat ejector to a wing structureto improve its high angle of incidence performance and margin of stall.The ejector is fed a primary fluid from e.g. a gas generator, and it isposition such that it streamlines the flow over said airfoil to delaystall.

FIGS. 16B through 16D show different angles of the illustration shown inFIG. 16A, with details of the positioning of the ejector on the wing,the plenums supplying the primary fluid to the ejector, and theirrelative position to each other and the airfoil.

The ejector described in FIG. 14 is flat in geometry and it contains anupper and a lower portions, both introducing the motive fluid as walljets in a multitude of slots and generally perpendicular to the jetefflux direction of the flow or streamlines, elements 1401 and 201 whichcan independently rotate around axes 102 and 202. The curved walls namedCoanda walls 103 and 203 allow for the primary jets to follow thecurvature and entrain in the process and at a ratio exceeding 3:1,secondary air, generally arriving from the flow above an airfoil such asa wing's upper surface boundary layer. The primary nozzles 104 and 204are of various shapes with various 3D effects to maximize theentrainment ratio such as delta mini-wings 212 in FIG. 22B, or may befluidic oscillators fed by said plenums supplied with motive fluid togenerate a pulsed operation of motive fluid injection over the Coandawalls. The mixed fluid arrives at the throat area (minimum area of theejector) to a pure axial direction. Beyond this point, the currentinvention introduces a segmented, movable diffuser section such as aflap only that it has a major role in the performance of said ejector byvectoring and/or maximizing its performance.

For example, at take-off, the inlet of the said ejector is fixed andstill above an airfoil 1700 in FIG. 17A pointing forward. FIG. 17Adepicts the deployment of such ejector formed by a lower (1401)semi-ejector and upper (201) ejector and in conjunction with the mainwing of an aircraft of a drone. The two semi-ejectors can rotate aroundaxes 102 and 202 respectively and can also translate according to themission requirements. FIGS. 17B and 17C show the case where only theupper semi-ejector 201 is actively used with a primary fluid, whereas1401 is replaced by a simple flap. As before, 201 can rotate around axis202 and translate relative to the axial position. The semi-ejectorsreceive the primary fluid under pressure from e.g. a gas generator suchas a gas turbine and allow its passage through primary nozzles, whichmay employ fluidic oscillators (i.e. pulsating at certain frequenciessuch as up to and including 2000 Hz to generate a pulsating entrainmentof the secondary flow).

In FIG. 14, the ejectors upper half diffuser 210 is extended to form acurved surface 210 a and guiding the mixed primary and secondary flowsdownward. At the same time, the lower diffuser 110 is also extended into110 a, maintaining the appropriate ratio of area growth and mixingcharacteristics to obtain the maximum thrust required by the aircraft.Some portions of 110 a and 210 a may not be deployed and the 110 and 210are controlled independently yet according to an appropriate schedule.In addition, the upper 201 element may or may not be moved axially tofollow the needs of the mission. In one embodiment, different amounts ofprimary fluid and/or delivered at different conditions may be suppliedto the upper 201 or lower 1401 elements in a continuous or pulsedfashion. The 110 a and 210 a diffusor surfaces may contain dimples andother elements that delay or avoid separation of the boundary layer.Additional, secondary nozzles may also open if the fully extended 110 ais utilized, at particular locations and potentially staggered and maybe pulsed according to fluidic oscillators operation modes to supply apulsed operation mode to the ejector.

When fluid is received from a compressor bleed, the motive air is lowerin temperature. The exhaust gas from the hot end of the gas generator(exhaust from turbine), for example, for motive gas temperatures of 1500F at pressure of 30 psi compressor air discharge and the entrainmentratio of 5:1, and ambient temperature of 100 F, the temperature of themix becomes 335 F (180 C), for which the density of the air is 1.6E-3slugs/ft3 or 0.84 kg/m3, a drop of ˜30% from ambient. As such, theoverall wingspan can be reduced by ˜10%, even taking into the accountthe density reduction effects, when an airfoil is deployed behind themain propulsor. For entrainment rates of 10:1 (better than the 5:1design), for similar conditions and an emerging jet of 125% of theairspeed of the aircraft, the lift benefit is higher because the mixdensity is now larger, at ˜200 F mix temperature and lift generated overthe wingspan washed by the jet is ˜16%. In this example the wing can bereduced in length accordingly.

Thrust Generator

Another embodiment of the present invention relates generally to a novel3D thrust generator which is capable of receiving pressurized gassesfrom a plenum, entraining ambient air at still or moving conditions(including but not limited to those conditions greater than 0.05 Mach),accelerating the air via momentum and energy transfer with the highpressure gasses, and directing the well mixed fluids to a high speed,non-circular efflux jet with mostly axial direction velocity component.The efflux jet can be a mixture of hot, high energy gases, provided tothe thrust generator via conduits from a high pressure gas generatoroutlet, and entrained ambient temperature air. The entrained air can bebrought to high kinetic energy level flow via momentum transfer with thehigh pressure gasses supplied to a propulsive device, inside the thrustgenerator. The resulting mixture of air and gas emerges out of thethrust generator and pointing mainly in the axial, downstream direction,opposite to the direction of vehicle trajectory. The well mixed streamprovides a mostly unidirectional stream of colder gas at high velocity,which can be used for propulsion, hovering, lift generation and attitudecontrol via airfoils placed in the wake of colder jet. This is not seenin any conventional jet fuel engine propelled vehicle. This thrustgenerator may be stand-alone off the fuselage, embedded with thefuselage in the front or the back of the vehicle, and/or embedded in thewings for stall margin improvement.

Reznick invented a circular device with the primary nozzles beingdetached from the Coanda surface and hence, not generating wall jets.While Reznick teaches that additional secondary fluid is being admitteddue to the offset to the Coanda surface, its application, however, isstrictly circular in shape and thus, cannot be scaled up in a morepractical application for aircraft of larger flows and, for instance,still be integrated with a wing, as drag increasingly becomes larger. Inaddition, the slots also appear to be simple in geometry and notpresenting any particular 3D features for mixing enhancements. Thepresent invention introduces a streamlined propulsor that generates anefflux of rectangular shape at the exit plane, in order to use theenergy for additional lift generation in the thin airfoil, animprovement and departure from Reznick's circular application, whichcannot be effectively used along a longer airfoil for lift generation inlevel flight other than its own diameter, and cannot be deployed over awing to ingest the boundary layer of a wing, as one of the embodimentsof the present invention.

Primary Nozzle Geometry.

It is noted that in all the described patents the inventors are notemploying any features that would increase the area of the primary jetto the secondary flow, and therefore limitations of the describedinventions exist. In addition, no staggering of primary nozzles in theCoanda device exists, with exception of Throndson's presence of thecentral primary nozzles, which are not placed on the Coanda device butinstead in the center of the inlet perimeter of the Coanda primarynozzles. The primary nozzles are therefore in general placed in the sameaxial plane and not staggered, nor are they different in size from theadjacent ones but of the same size and shape. If for a circular Coandadevice this is optionally advantageous, for a non-circular one which hasa constant gap between opposite sides of the Coanda primary nozzlesalong the length of its inlet plane largest dimension the thrustresulting form it would be equally distributed in an ideal situation butduring level flight, if such a device is employed for thrust generation,the secondary incoming air would unevenly be admitted into the deviceand therefore the thrust generation will impose challenges to the wingstructure and its design. This is mainly because in the aforementionedprior art, it was envisioned that these devices were used at the initialand final stages of the flight of an aircraft and not as a single,thrust generation propulsor for the entirety of the mission, fromtake-off to landing and including hovering and level flight. Indeed,Throndson's invention is applicable for vertical take-off only andlanding and hovering, with the main power plant taking over the levelflight function of providing thrust via a turbojet or turbofan. Hence,in his invention, the devices including the Coanda ejector are shut downand forming the airfoil of the wing in level flight, i.e. not operativeor active during level flight, after transition from take-off. On theother hand, Reznick teaches a circular device with primary nozzles forthrust augmentation but without embedding it with a wing for levelflight and exploiting both the intake and exit of the device for otherthan generating thrust, which is the present invention.

FIGS. 18A through 18E show conventional arrangements for Coanda-typeejectors. FIG. 18A depicts a traditional Coanda ejector of circularshape from prior art. FIGS. 18B and 18C show a flat Coanda type ejectorembedded in a wing from prior art. The source of the primary fluid is agas turbine and the ejector is optionally advantageously meant to beused for vertical take-off and shut off in level flight. FIGS. 18B and18C encompass the elements disclosed as variables of Throndson,including diameters, angles and lengths.

FIG. 18D is FIG. 3 of Reznick and shows another circular embodimentwhere hypermixing nozzles are employed and the primary fluid nozzles areaway from the walls of the ejector. Hence, the primary jets are nolonger wall jets. Reznick only covers the circular geometries of theejector, clearly meant to be used for take-off assistance due toscalability limitations.

FIG. 18E depicts one embodiment of the present invention with circularCoanda nozzle elements, with a plenum 211 supplied with primary fluid,which is accelerated through primary nozzles 203 and injected as walljets over surface 204.

Throndson uses a non-circular form of the ejector but also rectangularslots. A rectangular slot is useful in such an application but producesa limited surface for a shear jet entrainment of the secondary,approaching air. Indeed, a rectangular slot described by the inventorsabove produces a jet entrainment characteristic to a rectangular slotperimeter of the given dimensions, 2 L+2 h=2 (L+h) where L is the lengthand h is the height of each slot. A much larger quantity of secondaryflow is entrained if a larger perimeter of the primary nozzle is used,including the impact of 3D features. Staggering axially the vertices ofa zigzag or wavy (sinusoidal) walls of a primary nozzle as shown inFIGS. 18A through 18E greatly enhances the entrainment of secondary airas taught in the present disclosure. A pulsed operation via embeddingfluidic oscillators with the primary nozzles further enhances theefficiency and entrainment characteristic of the ejector.

FIGS. 19A through 19D depict some of the proposed changes in primarynozzles for better performance. FIG. 19A shows a zig-zag configurationof primary nozzles along the circumference of the inlet area of theejector, whereas the primary jet perimeter exposed to the secondary flowis doubled compared to a simple slot perimeter, hence increasing theentrainment via turbulent shear layers developed in-between said zig-zagwalls of the primary nozzles. FIG. 19B shows a rectangular slot withincreased, roughened perimeter to generate additional turbulence, andhence increase entrainment 1.5-4 times compared to the original, smoothwalls of a rectangular slot. FIG. 19B describes schematically theincrease of the area of the primary jet surface to the secondary orentrained air, with the 3D structure of the spikes explained in axialdirection. While normally in a rectangular slot arrangement thesecondary air is entrained mainly in between two adjacent slots and onthe outer radius slot side, the entrainment is greatly enhanced now viasurface and 3D effects. FIG. 19C explains the primary jets and secondaryjets respectively, with the turbulence generated by the 3D featuresgreatly improving the mixture and momentum imparting of the primary flowto the secondary flow in a shorter distance. FIG. 19C shows theinteraction and flows resulting from said adjacent rough wall slots,with red arrows depicting the primary fluid and the blue arrows theentrained, secondary fluid. Shear layers are formed along the walls andthe increased perimeter results in significantly higher entrainment ofsecondary flows for the same input, primary flow conditions. Pulsedoperation of the primary nozzles further enhance the entrainment ratio.

Another feature one embodiment of the present invention is theintroduction of advantageous features inside the primary nozzle (seeFIGS. 19E and 19E). It is well known that a flow over a delta wingproduces vortices that are opposed in direction towards the center ofthe delta wing. A miniature feature is placed in some or all of theprimary nozzles to generate such vortices that emerge from the primarynozzle. In this case the vortices advantageously entrain significantlyhigher amounts of secondary air into the ejector, enhancing its mixtureand the imparting of momentum carried by the primary fluid coming out ofthe primary nozzles in a continuous or pulsed manner.

FIG. 19E explains the flow over the delta wing obstruction placed insidethe primary nozzles in its center, which changes the pattern of the flowsuch that it increases significantly the entrainment ratio of a normalprimary nozzle slot, without requiring changes in the flow rates ofpressure and temperatures. In particular, the primary vortex cores areopposed in direction towards the center of the said slot or delta wing,entraining significant secondary fluid from the area in between theslots.

FIG. 20 describes the thermodynamic cycle of the current disclosure withthe evolution of the working and entrained fluids to obtain a highthermodynamic efficiency. FIG. 20 demonstrates that entrainment of airwill determine the movement of point D which represents the mixingcondition between the primary gas and secondary air, in a propulsionthermodynamic cycle diagram, to the left and at lower values ofTemperature and entropy. This is optionally advantageous for a highpropulsive efficiency device, where massive amounts of air are entrainedand accelerated to relatively lower exit jet velocities, maintaining ahigh thrust level due to higher mass flow rates, a key ingredient torealizing high propulsive efficiency. In FIG. 19A, an increase in theperimeter by a factor of 2 is showed by replacing each length of anormal rectangular slot perimeter with a 2× longer perimeter equilateraltriangle in the same plane. The perimeter can be further increased bystaggering all vertices of the slot walls in various planes (see FIG.19B). The result of such a primary nozzle is to increase the amount ofthe fluid entrained as secondary fluid by at least 15-50% throughintimate mixing inside the formed shear layers. If the secondary airinitial condition was of low speed, then the performance of therectangular and non-rectangular perimeter shapes may be not verydifferent, however, when the ejector is moving forward and approachingsecondary air velocity is significantly larger, such as between Mach 0.0and Mach 0.25, then the spiked profile shape of the primary nozzle mayalso improve significantly by placing the inner most and outermostspikes of the primary nozzle ahead and behind the axial plane of thesaid rectangular slot. In other words, each primary nozzle becomes now a3D structure which will delay or anticipate the entrainment of thesecondary air in an efficient manner hence improving the overallentrainment rate. In a Coanda ejector it is optionally advantageous thatthe secondary air entrainment and mixing with the primary air formomentum transfer happens fast and over a short distance. Adding thisand other 3D elements to the primary nozzle help improve the performanceof said ejector.

Another feature related to primary nozzles as employed in thisembodiment is the introduction of fluidic oscillators within the primarynozzles flowpath. These fluidic oscillators provide e.g. up to 2000 Hzswitches between two adjacent primary nozzles to alternate the wall jetflows and improve entrainment rates via pulsed operation of the motivefluid.

Yet another feature implemented in this invention is the staggering ofthe nozzles with its features, by being placed at various locationsalong the Coanda surface and hence via introduction of the primary flowat multiple axial locations, adjacent to the wall in a wall jet mannerand in a pattern that increases the entrainment and mixing of thesecondary fluid. For example, FIG. 21 shows such an embodiment where aV-shaped, vortex generating feature is staggered when compared to anormal rectangular slot and injecting at least 25% of the total theprimary fluid before the balance of the primary fluid massflow isinjected at a moment later. This injection prior to the rectangularslots results in a higher entrainment rate enough to increase theperformance of the ejector significantly. Moreover, in FIG. 21, theprimary nozzles 205 inject the primary fluid before the 203 primarynozzle. Primary nozzle 205 has a feature that introduces a morefavorable entrainment of the secondary flow via shear layers and thesenozzles 205 are staggered both axially and circumferentially whencompared to the primary nozzles 203. Primary nozzles 203 have a deltawing feature that is provided with a supporting leg connected to themiddle point of the primary slot structure at the inner most side of itand having the delta wing structure pointing against the primary fluidflow to generate 2 vortices opposed in direction and strongly entrainingfrom both sides of primary nozzle 203 the already entrained mixture ofprimary and secondary fluid flows resulting from nozzles 305. Thevortices and V structure of the primary nozzles result in an improvementof entrainment of 10-100% compared to the rectangular, non-staggeredslots and an overall improvement of the momentum transfer from primaryto secondary flow.

Furthermore, FIG. 21 depicts a simpler construction using delta wingletspaced inside smooth wall slots to form specific delta wing flows andshear layers that advantageously increase the entrainment ratio by morethan 2 times compared to the smooth wall rectangular primary slots. Allthese elements can be combined for the best entrainment ratio. Thepresent invention improves the surface for flow separation delay viaelements 221. By placing dimples on the Coanda surface 204, where saidCoanda surface 204 has a relatively aggressive turn for the shortestdistance change of primary flow direction, radially originating fromprimary nozzles 203, to axial direction opposite to thrust direction,towards the throat 225. The dimples prevent separation of the flow andenhance the performance of the ejector significantly, in conjunctionwith the delta turbulators shown in FIGS. 19D and 19E.

FIG. 23 illustrates certain features according to an embodiment of thepresent invention. In particular, FIG. 23 compares a similar primaryslot height used by Throndson with the ratios used by Throndson todemonstrate the improvement of this embodiment of the present invention.The radius of turn to slot height of this embodiment is below 5:1 withimproved separation delay dimples placed on the Coanda surface. In FIG.23, the radius R′ is about 2-3 times smaller than the R radius frompatent by Throndson, for similar slot heights. It follows that a smallerthan 5:1 ratio is possible, due to use of a logarithmic profile inconjunction with the employment of dimples on the curved, Coandasurface, to turn more aggressively the flow from pure radially at theexit from the primary slot to purely axially at the throat. As a result,a much faster turn without flow separation follows, so the throat of thedevice may be larger than that specified by Throndson by at least25-100%. The half angle of the diffuser can also be made significantlymore aggressive than in prior art, allowing for a much shorter diffuserto be implemented and more rapid momentum transfer between the primaryand secondary flows. As such FIG. 23 highlights the differences betweenthe present invention and the prior art, especially where moreaggressive elements such as turbulators, primary nozzles, dimples andmovable walls improves the prior art.

Coanda Ejector

In general, the design of a Coanda ejector as applied to an aircraft hasbeen described by many publications. For example, U.S. Pat. No.3,664,611 (Harris) teaches a Coanda type ejector embedded in the wingfor vertical take-off and landing purposes. The device is not activeduring cruise, see FIG. 24. Harris is silent on the use of the effluxfor generating more lift in a tandem type arrangement. Moreover, Harrisdoes not apply the device for use in level flight conditions. Rather,consistent with conventional practices, the device collapses into anairfoil wing during level flight conditions.

Mocarski, on the other hand, teaches that in a Coanda ejector, theprimary, high energy fluid, also called motive fluid, is injected as awall jet and the principle of such a device is to determine a lowpressure zone where ambient air is entrained, followed by a mixing,converging zone towards a throat, followed by a diffuser to expand themixture back to the ambient pressure at high velocity. U.S. Pat. No.3,819,134 (Throndson) modifies and improves on this concept described inMocarski.

Throndson describes an enhancement of the technology by adding a primaryflow into the center of the Coanda type ejectors to further entrainsecondary fluid and to enhance the performance of the nozzle, with theprimary, central nozzle using 30-70% of the total primary fluid and thebalance being used in the Coanda-type, parametric nozzles. Throndsonclaims that the thrust augmentation is greatly enhanced by thiscombination, and not commenting on the primary fluid nozzles geometry,which appears as simple slots or orifices. In addition, the slots appearto be continuous or discontinuous and without special features.Throndson is silent about the use of the efflux jet for lift generationdownstream and indeed, it only employs the device for take-off andtransition and landing, not for cruise conditions, much like Harris.

The present invention further improves the Coanda ejector by generatingthrust at all flight conditions via swiveling of the Coanda device andby placing a thin airfoil in the jet efflux hence generating more lift.Such turbofans generally employ at least two advantages over Harris andThrondson:

First, the use of the ejector downstream of a wing such that it ingestsits detrimental boundary layer at cruise conditions, improving thewing's aerodynamic performance and allowing high angles of incidence,hence increasing its overall performance. The present invention alsoallows the operation of the ejector in all phases of flight, fromtake-off through hovering, transition, cruise and landing. Oneembodiment also allows the use of a semi-ejector (½ of a flat ejector asdescribed by Throndson or Harris) in conjunction with a flap of a wingto form a non-symmetrical Coanda ejector with the entrainment of theboundary layer only at the outer edge of said boundary layer and forminga diffuser with said flap of the wing, including vectoring the thrusterby moving the flap and the air knife type Coanda ejector in coordinationfor take-off and landing.

Second, by using a thin airfoil downstream of (in the wash of theejector) at a minimum in level flight but also for other conditions offlight for additional lift generation in a higher speed stream, itallows the airfoil and propulsor tandem to be more compact and efficientwhile generating considerable lift, as compared to those disclosed inthe aforementioned patents. In this embodiment of the present invention,the shape and profile of the propulsor efflux jet is critical toachieving its novel efficiency and functionality. The said thin airfoilis placed at convenient distance from the exit plane of saidejector/propulsor in order to maximize the lift but also before theefflux jet's energy is dissipated to the ambient. This is convenient andpractical as the energy of any jet propulsion device usually dissipatesonly over very long distances behind the aircraft.

It is also of importance to understand that both elements of said tandemneed to work together in an efficient and optimized manner, includingmoving at certain angles and rates favorable to the concept. Thethruster/propulsor transmits mechanically the thrust component to thefuselage of the aircraft or its main wing, whereas the thin airfoildownstream of the propulsor is in mechanical contact with the fuselageand not the propulsor, yet receiving its efflux jet in such manner thatit maximizes the lift of the aircraft and allows for maneuvering viamovements of certain surfaces on said thin airfoil.

Another feature of the present invention provides for the capability touse of the same nozzles for lifting the aircraft hovering and landing aswell as for cruise purposes. The lift system disclosed in U.S. Pat. No.8,910,464 (Ambrose) represents the common backbone of the VTOL jetfighters. It has limitations due to the extra weight carried around incruise mode, namely the lift fan and its auxiliaries. Under current VTOLtechnology, the cold nozzles (forward nozzles) and the lifting fan areshut down during level flight which leaves the main exhaust nozzle toprovide the reaction force to propel the aircraft forward at forwardmoving conditions such as cruise. One embodiment of the presentinvention combines Coanda nozzle thrust generation elements with thepropulsive system of the aircraft allowing the ejector to be employed atall stages of flight with weight minimization and elimination of movingparts. Moreover, it enables the use of such an ejector to minimize dragand maximize lift in a unique manner during level flight.

Mocarski presents the same technology for Coanda device with continuousor discontinuous primary fluid slots, mainly circular or linear. In allthese patents the Coanda surface is a circular or 2D smooth profile todetermine a simple boundary layer attachment without particular elementswhich can enhance the entrainment, increase the aggressive turn of theCoanda surface or delay its separation. In ejectors of Coanda type it iscritical that the turn of the surface that allow the boundary layer ofthe wall jet to grow and mix with the secondary air and not becomeseparated. Once the primary flow jet from the primary nozzles becomesseparated, the Coanda ejector will not operate efficiently or at all. Itis therefore paramount that the surface curvature is such that allowsfor maximum boundary layer growth and entrainment of the secondary fluidand mixing with it, without separation at the wall.

On the other hand, if the curvature is too large, the device becomesimpractically long and large in diameter, restricting also the amount ofthe secondary fluid entrainment and mixing and inducing a very longdiffusing portion of the device. The ratio of slot to the radius of theCoanda turn is described by Throndson to be between 1:5-1:15, but aratio smaller than 1:5 should be ideal for rapid turn. The turn of theCoanda curve is clearly stated by Throndson to be ideally between 30-110deg. compared to the axis of the device. If the diffusing section isbecoming too large, this is an important limitation in deploying thetechnology for an aircraft in level flight, as the length of thediffuser would impose significant additional drag and weight on theaircraft. Should the turn become >110 degrees, then the diffusor maybecome shorter and enhance the mixing on a much shorter distance,assuring the intimate mixing and energy and momentum transfer to thesecondary flow before the exit of the mixture from the device. It isnoted that the walls of the diffusor are also flat and without 3Delements for enhancement of the mixing process. One embodiment of theinvention introduces moving walls past the throat section, especially inthe diffusing area of the ejector, in a manner favorable to the verticaltake-off and landing of an aircraft, without the need to move the entireejector around its horizontal axis but rather by extending the segmenteddiffusor surfaces in a manner described below.

Coanda Surface.

The Coanda surface, as taught by Reznick, Mocarski and Throndson, shouldbe a round curvature, with Throndson providing even more precise detailsthat the range of ratios of slot height to radius of 1:5 up to 1:15. Alogarithmic profile is preferred by those skilled in the art, since itprovides the fastest boundary layer growth without separation of thewall jet. However, one embodiment of the present invention achieves afar more aggressive turn by introducing dimples on the Coanda surface tosignificantly improve the turn of the surface in order to keep the flowattached while mixing and moving the mixture into the throat anddiffuser. An aggressive turn is preferable because it allows for theability to quickly mix and turn the flow in the axial direction, throughthe throat and into the diffuser section. The turn of fast movingfluids, in fact, can keep the boundary layer attached, while theboundary layer grows and mixes with the central flow.

The dimples in the present invention may be of different sizes, may bestaggered or aligned, may be located in areas where the turn is moreaggressive and not in areas where the turn of the fluid is lessaggressive. The dimples may also be employed on a more aggressivediffuser, where the half angle of the diffuser is not constant butvariable, growing and then reducing to 0 as depicted by element 105 inFIG. 14.

FIG. 14 depicts one of the improvements achieved by the presentinvention, especially when compared with Thorndson. FIG. 14 compares asimilar primary slot height used by Throndson with the ratios providedin Throndson to demonstrate the improvement of the current invention. Inparticular, FIG. 14 shows the upper and lower halves of semi-ejectorsthat together form a better, more flexible and performant ejector thatcan be suited both for vertical take-off and hovering and for levelflight at cruise conditions. The lower (1401) semi-ejector wall is moreaggressively utilizing the primary nozzle wall jets to turn moreaggressively the flow around axis 102 and over the surface 103, a Coandainlet surface. The maximum height point of this curve is axiallyposition at a point about ‘G’ distance from the similar lowest positionof the curved wall (closes to the axis shown in blue) of element 201.Hence, the two semi-ejectors (or airknife ejector walls) 1401 and 201are staggered, i.e. their inlets are not positioned axially at the samelocation. Similarly, the minimum distance axial location of 1401 and of201 is staggered by distance ‘G’, their diffusers 110 and 210 can changeshape by means of actuators 115 and 215 respectively, where the flatsegmented surfaces forming 110 and 210 become a curved cross section 110a and 210 a respectively, directing the flow inside the said ejectordownwards or in various directions as dictated by the mission. FIG. 14also depicts the changes in ratios compared to prior art.

Furthermore, the radius of turn to slot height of the current inventionis below 5:1 with improved separation delay dimples placed on the Coandasurface. As a result, a much faster turn without flow separationfollows, so the throat of the device may be larger than that specifiedby Throndson by at least 25-100%. Moreover, by applying a constantvariation of the half angle of the diffuser part (i.e. non-linear growthof the wall away from the centerline) and employing dimpled surface intothe said diffuser, its dimension may grow without separation of the flowmore aggressively, resulting in a shortening of the overall length ofthe device.

In addition, if both the upper and lower half of the ejector actseparately with respect to fluid supply and functionality, but are ableto work together for entrainment, mixing and diffusing of the mixture tothe exit plenum, then the performance is greatly improved by theadditional diffusor moving walls on both upper and lower surfaces of theflat diffuser. This, in turn, also allows the more compact device to beimplemented in conjunction with a wing structure for propulsion reasonsin level flight or vertical take-off, hovering and landing with no needto rotate the entire structure.

Moreover, the use of dimples allows a variation of the wall from theinitial point until the exit all around the perimeter of the saidejector, hence allowing good integration with the wing structure. Adifferent structure is used at the round ends of the ejector, wheredimples or special features on the primary nozzles may not be requiredfor the ejector to perform satisfactorily. FIG. 22A shows an ejectorthat has significant 3D features as described in this invention. Inaddition, in the most aggressive zones of the turns on the lower wall ofthe diffusor, the use of dimples (element 221 in FIG. 21) will alsoallow a greater turn to up to 90 degrees downwards or even more. This ismore aggressive than the prior art (e.g., Throndson; see Fernholz, H. H.“Z. Flugwiss. 15, 1967, Heft 4, pp 136-142). FIG. 14 shows a crosssection of an ejector that has significant 3D features as described inthis disclosure. FIG. 14 also shows mostly-segmented walls on thediffusor, able to redirect the ejector efflux jet and to maximize itsperformance from the changes in the diffuser areas and mixing zones. Theinlet plane of the ejector is not lying in a plane (not planar), andhence it is possible to place the ejector above a wing structure suchthat the ingestion of the boundary layer is improving the wing airfoilperformance, as it can be seen in FIG. 14 with dimension G (gap) betweenthe two inlets of the upper and the lower ejector halves. The Coandasurface (104 in FIG. 14; 204 in FIG. 22A) is hence not admitting theprimary fluid wall jets at the same axial position, but sooner at theproximity of the airfoil surface and later away from the wing airfoilsurface, in the axial time-history direction.

FIGS. 22A through 22F illustrate different embodiments of the presentinvention, where 3D features are used in the inlet. FIG. 22F features anupper semi-ejector. FIG. 22B shows the element 212 as a delta turbulatorplaced inside a primary nozzle, that enhances considerably theentrainment of secondary flows, and dimples such as 222 that enhanceattachment and prevents separation even at most aggressive turns of theCoanda curved wall 203 of FIGS. 22A through 22F, and FIG. 14.

In FIGS. 22A through 22F, element 212 is also introduced in the primarynozzles to enhance entrainment and they may be employed or not on theopposite side of the ejector, depending on the conditions and to enhancethe performance. Dimples 221 are placed on the contour 204 and thediffuser to guarantee a good momentum transfer in the shortest lengthand generating as uniform as possible exit velocity and temperatureprofile of the mixture of primary and secondary fluids and avoidseparation of the flow. These primary fluids may be pressurized air froma compressor bleed or pressurized exhaust gas from a gas turbine or amixture of both and can be fed to the upper and lower ejector halves1401 and 201 separately, adding another degree of freedom on maximizingthe efficiency of thrust generation.

In FIG. 22A, 3D features increase the perimeter exposed to the flow andallowing for higher entrainment ratio. In FIGS. 22B and 22C, speciallydesigned turbulators, such as a delta wing placed in the center of theprimary slots, cause the flow from the primary fluid plenum, suppliedconstantly by, e.g., a gas generator, to be accelerated in a passage andforced to flow over the said delta turbulator 212. The element 212forces the flow into patterns that greatly improve the entrainment ofsecondary flow via a series of mechanisms including shear layers,rotating and counter-rotating turbulent flows and increased wettedperimeter of said primary slots 203. Embedding fluid oscillators withinthe primary nozzles provides also additional capability for entrainmentvia pulsed operation on adjacent primary nozzles.

FIG. 25 shows an arrangement of the ejector with the advantage of havinga 3D inlet with the lower lip (22) of the ejector that is closer to theupper airfoil wall side 20 and beyond the apex of said airfoil,staggered axially and positioned ahead of the upper lip (23) of saidejector further away from the airfoil surface 20. The position of thelips are modeled to match the most probable boundary layer velocityprofile (21) resulting from airflow near the airfoil. By anticipatingthe entrainment of the stream closes to the airfoil wall with lip 22,compared to lip 23′s entrainment of the boundary layer, a betterdistribution at the inlet and ejector performance is obtained. In oneembodiment of the present invention, the ejector can be moved up anddown (in the vertical direction to the upper airfoil wall) to optimizethe performance. This will allow for a better performance of the airfoilat higher angles of attack and a better performance of the ejectoritself, by a better entrainment process. The 3D elements thatdifferentiate this disclosure from prior art include the position of theinlet lips 22 and 23, the relative position of the curved walls 204, thepositioning of the throat area 24, and of the diffuser walls 25. In oneembodiment, the two halves of the ejector can independently moverelative to each other and the airfoil, resulting in a constantlyoptimized position with respect to the performance of the aircraft.

FIGS. 17A through 17C show a flat ejector placed on the airfoil thatforms a wing and having two halves that can move independently (see FIG.17A) and also an embodiment where only the upper half of the ejector isused similar to an air-knife but forming a throat and a diffuser with aflap of the wing place on the airfoil, matching the performance needed(see FIG. 17B). In these embodiments, the flap may or may not containprimary nozzles, and the flap moves independently from the upper ejectorhalf, also described as an airknife. The advantage of such a system isthat it is simpler, it still allows high angles of incidence on the wingas explained in current disclosure by avoiding the wing stall viaingestion of the boundary layer, and the potential to rotateindependently the flap and the airknife for optimized performance andmaneuverability.

In particular, FIG. 17A shows the embodiments of a flat ejector asdescribed above with elements such as dimples onto a wing behind theapex of the wing and such that it mostly ingests the boundary layerabove the upper surface of the wing. FIGS. 17A through 17C, on the otherhand, show the use of an air knife type of ejector which forces ingestedair (as secondary fluid) from above the wing to accelerate and propelthe aircraft forward. In all these embodiments the ejectors may swivel.Moreover, in another embodiment, the ejectors' inlets may also swivel ina limited manner, but their diffusor walls can extend as furtherexplained in FIG. 14, changing angles, areas of exhaust, etc. asdictated by the conditions of flight. 1401 and 201 can independentlyrotate around axes 102 and 202 respectively.

-   Fluidic Propulsive System and Cycle.

Yet another embodiment of the present invention relates generally to apropulsive cycle and system that provides thrust via fluidic momentumtransfer. The propulsive system consists of a 1) gas generator thatprovides several streams of high pressure air or gas sources to 2)conduits network that direct the said compressed fluids to 3) augmentingthrust generation elements installed on the aircraft at variousstations. The augmenting thrust generation elements direct a high speedefflux jet with mostly axial direction velocity component in the desireddirection, hence generating an opposing thrust force. The efflux jet isa mixture of hot, high energy gases, provided to the thrust generatingelement via conduits from the high pressure gas generator locations suchas compressor bleeds, combustion bleeds, turbine bleeds and/or exhaustnozzle, and is such engineered to entrained surrounding air at verylarge rates of entrainment. The entrained air is brought to high kineticenergy level flow via momentum transfer with the high pressure gasessupplied to said thrust generating element, inside the thrust generatingelement; the resulting mixture of air and gas emerges out of the thrustgenerating element and pointing mainly in the axial direction, towardsthe said thin airfoil leading edge and mainly pressure side of theairfoil preferably in the direction to maximize lift on said downstreamairfoil.

FIG. 29 illustrates one embodiment of the present invention, featuringthe propulsion device in VTOL configuration. The ejectors 801 and 901are oriented downwards and the thrust is moving the aerial vehicleupwards. The ejectors are rotating in sync and flow of primary fluid ismodulated to match the need of thrust to forward and aft ejectors fromcompressor bleeds for the ejectors 801 and exhaust gas for ejectors 901.

The most efficient conventional propulsion system for medium and longdistance aircraft engines is the high by-pass turbofan. Conventionalturbofans employ at least two shafts, one common to the fan and lowpressure turbine, and one common to the core, which may consist of abooster, a high pressure compressor and a high pressure turbine. Thehigh efficiency of a turbofan is driven by high by-pass ratio, low FanPressure Ratios to determine a high propulsive efficiency; and by highOverall Pressure Ratios, for high thermal efficiency. The specific fuelconsumption of the aircraft is inversely proportional to the product ofthermal and propulsive efficiencies. The thermal losses in a turbofanare mainly due to combustion and thermodynamic losses in components suchas the compressor, turbine and mechanical efficiencies that are lessthan 100%. The combustion process irreversibility is, in general, themajor component leading to lower thermal efficiency and typical highpressure ratio power plants are only 40% thermally efficient.Practicality and other aircraft limitations (weight, drag, etc.) preventimplementation of methods known in the art for thermal efficiencyimprovement, such as intercooling, heat recovery and other.

The propulsive efficiency is maximized, on the other hand, when thepropulsor accelerates a largest amount of air mass flow at small axialvelocity, just above and as close as possible to the airspeed of theaircraft. This results in the need of having very large fan diametersand high fan speeds, increasing the drag and the weight of the aircraft.Currently, the most and highest efficiency turbofan is very large as thediameter of the fan is exceeding 11 feet in size. While the increasedfan diameter improves the propulsive efficiency, the drag increases dueto size of the cowling and a trade-off is generally performed to obtainthe ideal system. Current levels of propulsive efficiency exceed 85% andefforts are dedicated to distribute thrusters on wings to maximize it.One popular idea in the art is the concept of distributed propulsiveelements. The thrusters may be distributed on wings and fuselage of theaircraft. Mostly they are electrically or mechanically driven fansplaced on wings, and receiving the mechanical work or electric powerfrom a central unit. Such concepts are hard to implement due tocomplexity of the network involved, the weight of the electric motorsand their operability at high altitudes, and in case of mechanicaltransmission networks, efficiency, complexity and weight. The dominantdesign remains the two engine design.

One disadvantage of the current dominant design is that the turbofan isheavy and complex. More than 30% of its total weight is the fan systemalone, including the fan accessories and the low pressure turbine thatdrives it. Large rotating parts means that additional design limitationsexist, including limitations in tip speed, constrains on the lowerpressure turbine weight and dimensions, as well as inlet temperatures tothe Low Pressure Turbine. The fan blade needs to qualify and becertified in dedicated Fan Blade Ingestion and Fan Blade Out tests. Inaddition, the fan case needs to contain the liberation of such fanblades and protect the integrity of the aircraft. With smaller systems,the challenge of scaling down a complex turbofan system is significant,if efficiency is to be maintained. Particularly for UAVs and smallaircraft, the By-Pass Ratio (BPR) levels are much smaller due tolimitations in materials. As they shrink in diameter, fans need to spinfaster to retain their efficiency, and tip losses occur at higher speedsdriving lower efficiency. For small turbofans, the challenge is thatscaling down the fan (and compressor) means that the rotational speedhas to increase dramatically. Those familiar with the art understandthat the diameter of a fan scales directly proportional to the squareroot of the mass flow of fluid, while the blade tip speed of the fan isdirectly proportional to the product of the diameter and the rotationalspeed (e.g. Pi*Diam*RPM). Hence, if the diameter of the fan is reducedsignificantly then conversely the rotational speed needs to increase topreserve the same tip speed (for mechanical and compressibilityreasons), otherwise the losses in performance increase significantly.For example, if a 50 inch diameter fan spins at 2000 RPM, for same tipspeed a 20 inch fan needs to spin at 5000 RPM, and a 10 inch fan wouldspin at 10000 RPM and so on. This also implies that the Fan PressureRatio (FPR) would increase accordingly, driving a lower efficiency ofthe fan in the smaller diameter range. In addition, containment of sucha highly stressed fan component would be difficult to attain and itwould incur a thicker fan case, driving up the weight, and it woulddrive significant complications with respect to the rotor dynamics ofthe system and its bearing subsystem. This is why large fans are muchmore efficient than smaller fans. The status quo of small turbofans issignificantly less performing than larger systems, at least 3-4 timeslower than large fans BPRs and with higher FPRs, driving lowefficiencies (high fuel burn), high rotating speeds (high stress andmaintenance) and challenging operability and thermal management.Turboprops face the same challenge, albeit for really small systems theyhave the best propulsive efficiency. Their main disadvantage is thelarge size of the propellers needed to move massive amounts of air andmaking it difficult to implement in systems with VTOL capabilities. Themodern turboprop uses a low pressure turbine to drive the propeller andemploys additional auxiliary systems such as gears and bearings andtheir sub-systems, pitch control and other.

Another element of modern, aircraft propulsion jets such as turbofansand turboprops is that a certain amount of bleed air is required off thecompressor for cabin pressurization, turbine cooling and dischargeoverboard for operability of the engine itself. The compressor bleed airof a typical, modern jet engine is up to 20% of the total compressordischarge air. The compressor bleeds destined for cabin pressurizationare not needed if the aircraft flies at low altitudes or is unmanned,and this portion constitutes at least 10% of the total bleed. If theturbine is not cooled, then another circa 10% of the compressor aircould be extracted before it reaches the combustion, at the expense oflower firing temperatures and hence cycle efficiency. However, with theadvance of new non-metallic materials and their high temperature andstress capabilities, the turbine and indeed, most of the hot section maybe manufactured out of ceramic matrix composites, not only eliminatingthe need for cooling air but also allowing for higher firingtemperatures. For example, while the turbine inlet temperaturelimitation with current, uncooled metal components is known by thosefamiliar with the topic to be about 1750 F, current CMC materials couldsupport uncooled 2000 F turbine firing temperature or more. This resultsin a much higher efficiency cycle and in most cases a reduced weight ofthe engine, with overall benefits to the aircraft. If a 1750 F firingtemperature cycle, uncooled, all-metal components engine with 20%compressor bleed air is replaced by a 50% air bleed compressor firing at2000 F with ceramic components, then the efficiency of the cycle may becomparable, while 50% of compressed air is made available for otherpurposes, at the compressor discharge station.

TABLE 1 shows such a comparison for various air bleeds for two uncooledengines with same unit flow (i.e. 1 kg/s) and various bleed percentagesand same power output of the turbine supplying the required input powerto the compressor. The first line shows the pressure ratio of the cycle,the second line shows the compressor bleed, the metallic engine thermalefficiency calculation is shown on line 3 and the thermal efficiency ofthe CMC versions with similar bleeds and maximum bleed at sameefficiency compared with the metallic version are shown in the last twolines. The general assumption is that the turbine is uncooled in allcases, but air is bled off the compressor for other purpose. The tableshows that if the bleed percentage is maintained the same between themetallic and the CMC versions, then at a cycle pressure ratio beyond 8,the CMC engine becomes more efficient. Conversely, if the efficiency ofthe engine is to be maintained similar to the metallic one, the bleedair percentage can be increased dramatically. This can also be explainedby maintaining the same fuel flow to the combustion but reducing theflow of air until the firing temperature becomes 2000 F (CMC uncooledtechnology) from 1750 F (maximum metallic uncooled technology). Byproducing the same power outlet from the turbine to balance thecompressor power inlet, more compressor air can be made available forhigher firing temperatures. Based on this, the inventor has conceived acycle which allows a large quantity of compressor bleed to be routed viaa flow network and to supply an array of distributed augmenting thrustdevices placed in locations that enhance and improve current state ofthe art propulsive efficiency, at similar or better thermal and overallefficiency of the aircraft.

TABLE 1 PR cycle 4 6 8 15 Compressor 37% 43.5% 44.5% 42.2% Bleed 1750 F.uncooled 24%   26%   27%   29% metallic turbine engine efficiency 2000F. uncooled 24%   27%   28%   31% CMC turbine engine efficiency 2000 F.uncooled 44%   49%   50%   45% CMC engine compressor max bleed for sameefficiency as metallic turbine

Accordingly, conventional propulsors cannot be scaled down withoutsignificant compromise to their efficiencies. One embodiment of thepresent invention overcomes the current shortcoming through the use ofan improved cycle which eliminates the fan subsystem together with thelow pressure turbine. As such, this embodiment of the present inventiona system particularly suited for smaller aircraft systems and UAVs,particularly those that need to be capable of VTOL and STOL operation,because of its efficient, compact and highly integrated power plants.

The propulsor consists of a “chopped” fan and high pressure compressorplaced on the same shaft with a high pressure turbine to form a gasgenerator, a network of conduits connected to ejectors and the thrustaugmenting ejectors. The cycle utilizes a compressor system consistingof a chopped fan (core only pre-compression) and a high pressure singleor multistage compressor, preferably a centrifugal compressor withseveral bleed ports. The compressor bleed ports may bleed up to 50% ofthe total airflow in the system, with the remainder being directed to acombustor system. The combustion adds heat in the form of a fuel atconstant pressure or volume, and generates a hot stream of gas that isdirected towards a turbine. The high pressure turbine expands the hotfluid to a pressure and temperature lower that the turbine inletpressure and temperature in a conventional expansion process.Preferably, the turbine and the combustion are high temperaturematerials that need little or no cooling flows, such as modern CMCs. Theturbine, which can be either centripetal or axial in at least one stage,supplies the work needed to drive the compression system. The exhaustgas leaving the turbine is at lower pressures and temperatures than theinlet conditions to the turbine, but at least twice the pressure of theambient air and at temperatures typical of current turbofan low pressureturbine levels, i.e. 1500-1800 F. Thus, the expansion process of thehigh pressure turbine still results in a high energy, high temperatureand pressure flow that instead of being directed to a low pressureturbine, is directed via conduits to various location of the aircraft toa fluidic thrust generation propulsor.

The conduits may also be insulated and utilizing high temperaturematerials such as CMCs. The propulsor elements which are receiving thepressurized air or hot gases are employing fluidics for the entrainmentand acceleration of ambient air in a first section; and after mixing themotive fluid and ambient air and completing a thorough momentum transferfrom the high energy to the low energy (ambient air), accelerating themixed flow in a second, diffusing section, thus delivering a high speedjet efflux as a mixture of the high pressure gas (supplied to thepropulsor from a gas generator) and entrained ambient air at highspeeds, preferably and mostly in axial direction, with a certain axialvelocity profile known in the art. The entrainment rates of saidpropulsor elements are between 3-15 and up to 25 per each part of highpressure fluid delivered. Due to high entrainment and turbulent,thorough mixing of the flows, the jet efflux is accordingly much lowerin temperature. Following the law of physics with respect to mixing andmomentum transfer, the velocity of the jet efflux from the propulsorelement is close to but exceeding the aircraft airspeed. The jet effluxis also non-circular in nature, with little or no rotational components(as opposed to the large propellers of a turboprop or even a turbofan)and can be directed to airfoils to further recover some of its energyafter producing thrust, for example, directed towards the leading edgeof a short wing placed at certain distance behind the propulsor togenerate additional lift. In all embodiments, the gas generator is amodified turbofan where the fan has been chopped to provide only coreflow.

FIG. 26A shows a traditional bypass turbofan which bypasses most of theflow and mixes the core and bypass flows at the exit of the turbofan.FIG. 26B shows the turbofan with a chopped fan allowing for the coreonly and bleed flows off the compressor to produce the thrust needed forpropulsion. The bleeds off the compressor are conveniently locatedthroughout the cold section 2601 of the gas generator 800, as opposed toa hot section 2602 of the generator, such that it allows for maximumefficiency at any time during the operation. For example, at take-off,more bleed off the compressor may be required and a higher speed of therotor may be optionally advantageous. In this portion of the mission thebleed ports are open such that the compressor operation is away from thesurge line in a more advantageous condition than if no bleed waspresent. A current turbofan such as presented in FIG. 26A may only allowfor a maximum of 15% bleed throughout the mission, but by changing thechopped fan design in favorable ways, more core flow and more bleed offthe compressor may be induced in the present invention, up to andincluding 50% bleed of total air traversing the engine. Multiple bleedsmay also be involved, to enhance efficiency of the system, maximizingthe bleed at lower stages and minimizing the bleeds at higher pressure,as those who have the skills of the art would recognize. However, theamount of flow purposely involved in the cycle for bleeding only isparticularly applied in this invention. The bleed air off the compressorbleed ports is directed via conduits to the propulsors for augmentedthrust, placed in conjunction with the upper surface of an airfoil orimmediately behind an airfoil at high angle of incidence.

FIG. 27A illustrates an example of a bleed and conduits network embodiedin the present invention. The network contains a gas generator 800 thatfeeds several cold thrust augmenting ejectors 801 and hot thrustaugmenting ejectors 901 via compressor bleed ports 251 and 351respectively. Pressure and temperature sensors may take flowmeasurements as signals from elements 1702 (cold) and 1707 (hot) are fedto the micro-controller 900 (not pictured). The flow from the gasgenerator 800 to the thrust augmenting ejectors 801 via compressor bleedconduits 251 is dictated by control valves 1703, controlled by themicro-controller 900. The same controller dictates the actuation of theswiveling joints 1701 (for element 801) and 1705 (for element 901.) FIG.27A further shows a series of four (4) cold thrust augmenting ejectors801 being fed from the same ports 251 of the compressor of the said gasgenerator 800 and controlled by the micro-controller 900.

FIG. 27B depicts a similar network as illustrated in FIG. 27A, but withonly two cold thrust augmenting ejectors being fed by the compressorbleed ports off the gas generator 800. Swiveling joints 1701 allow forrotation of the elements 801 in multiple directions and may also allowfor the passage of the fluid to the said ejector 801. The position ofsaid ejector with respect to the aircraft is controlled via electric orpneumatic or mechanical means from a micro-controller 900. Sensors 1702for measuring the flow rate, pressures and temperatures in the conduitdownstream of bleed port 251 are used to feed the information to themicro-controller. In turn, the micro-controller commands the rotation ofelements 801 around the swiveling joints 1701 at the same time withcommanding the adjustment of the flow via the control valves 1703.Similarly, the thrust magnitude and orientation of elements 901 may beadjusted via adjustments in flow rates via the control valves 1707 andorientation adjustments about swiveling joints 1705 until the positionof the aircraft is acceptable. The controller is thus being fedinformation from the propulsion system conduit network, in addition tothe gas generator operating parameters and the orientation and magnitudeof the thrust on each of the thrust augmentation ejector.

FIG. 27C shows the micro-controller 900 and its network, depicting atleast twelve (12) inputs and at least four (4) outputs. The outputscontrol mainly the flow rate and the thrust (ejector) orientation tocontrol the attitude of the aircraft at any time in its mission.

FIG. 27D offers more details of the network. The flows from compressorbleed ports 251 and exhaust 351 are being fed to thrust augmentingejectors 801 and 901. Inputs to the micro-controller 900 include theparameters of the gas generator (rpm, compressor bleed air temperatureand pressure, exhaust pressure and temperature, etc.) via input 10.Inputs 26 include the feed from accelerometers included in the system.Input 30 is the gyroscope. Input 40 is an ultrasonic or barometricaltitude sensor input signaling the altitude of the aircraft. Input 50is the GPS input. Inputs 70 are the Bluetooth input. Inputs 80 are theR/C receiver.

In addition, FIG. 27D illustrates feedback from sensors on the conduits,shown as feed information 2702 and 2706, to the controller foradjustments of the flow via actuation of the control valves 1703 and1707. The control valves are connected to the controller via cables 2703and 2707 respectively, and they adjust based on the input received fromthe controller. The flow is adjusted and measured accordingly by thesensors 1702 and 1706, which provide feedback information to thecontroller to signal that adjustment was made accordingly. Similarly,the other sensors 10, 26, 30, 40, 50, 60, 70 and 80, either individuallyor together, are processed by the controller and adjustments of theejectors 801 and 901 positions are transmitted via cables 2701 and 2705.

In another embodiment of the present invention, the propulsor can beswiveled downwards to direct the thrust for changing the attitude of theaircraft for vertical take-off or short take-off. FIGS. 28A-28E showpossible shapes of a propulsor in the present invention. FIG. 28Aillustrates a relatively simple quadro-ejector system with the ejectorsbeing fed by a gas generator in the center. Two of the ejectors (cold)are fed from the compressor bleed ports with compressed air as motive(or primary) air, while the hot ejectors receive exhaust gas from theexhaust port of the gas generator. All four ejectors point downwards, inhovering mode, but adjustments of the attitude of the aircraft ispossible via changes in parameters mentioned in FIGS. 27A-27D. FIG. 28Bshows an embodiment of the present invention in which the device(s) canbe embedded in an aircraft. In FIG. 28B, only the two cold ejectors areshown (out of four). The ejector is flat, and placed behind the apex ofthe main wing, working to expand the stall margin of the main wing andgenerate a high-speed efflux for use in downstream lift generatingstructures. The flat ejector may also rotate along the main axis of thewing for hovering (pointing down towards the ground, mainly) or foradjusting the in-flight altitude. FIG. 28C illustrates a more complexcanard-type system consisting of four ejectors (two hot, tail located,and two cold, placed behind the canard airfoils) and the embeddedejector inside the housing system of the canard (cold) ejector side. Theejectors are flat and producing a jet efflux rectangular in shape attheir exit plane, mainly in the axial direction of the flight.Alternatively, an ejector having 3D elements is shown in FIG. 28D, wherethe inlet and throat and diffusor are 3D in nature (rather than 2D),which enhance entrainment and overall performance. Only an upper half ofa flat ejector is shown above the wing in FIG. 28E, pairing with theflap of said wing to form a complete structure with the primary fluidonly introduced at the upper half of the ejector (a half ejector, paringwith the flap of the wing).

FIG. 29 shows one possible arrangement of propulsion system at take-offor hovering in one embodiment of the present invention. The ejectors arepointing downwards to lift the airframe and maintain it in a hoveringposition.

FIG. 13 shows the maneuverability of a UAV equipped with a propulsionsystem. Pitch, roll and yaw positioning of the ejectors is shown, bothfor tail (hot) and cold (canard) ejectors.

In one embodiment of the present invention, the propulsors receivingboth the compressor discharge air (at least twice at the ambient airpressure) and hot gas efflux from the high pressure turbine (at leasttwice the ambient pressure) are in this embodiment pointing downwards attake-off, hence generating an opposing thrust exceeding the UAV weightfor lift-off U.S. Pat. No. 8,087,618 (Shmilovich et al.) discloses theuse of such a device embedded in the wing system and utilizing aturbojet engine exhaust for directing the exhaust or compressed air onlyat take-off and minor portions of the compressor bleed air (less than15% is mentioned) for additional flow control over a wing. Inparticular, they are not augmenting thrust but merely redirecting theexhaust stream by controlling it with compressed air during take-off.One embodiment of the present invention utilizes a specially designedpower plant that is particularly extracting the bleed air, in excess of20%, from the compressor and directing it to the said propulsorthroughout the flight, from take-off to landing. The particular way thisis achieved is by designing a compressor with more open first stagesthat can accommodate more flow, followed by bleeding of a portion of theflow in large quantities, such as up to 50% of total airflow, anddirecting this portion at all times to the cold gas propulsors, andutilizing the entire portion of the remainder flow for the thermodynamiccycle with the residual energy of the flow post-high pressure turbinedirected to a hot gas propulsor. The compressor bleed flows can also bemodulated via employment of flow controls, such as control valves orfluidic valves that modulate the delivery of the flow to propulsors.Both types of propulsors, cold and hot, can be swiveled at least from 90degrees to 120 degrees pointing down and up compared to the forwarddirection of flight and independently. The cold gas propulsor may beembedded with or hidden into the wings or preferably in the wake of avery high incidence angle first wing (canard wing) and enhancing itsstall margin significantly by placing the inlet of the propulsor inproximity of canard airfoil and preferably in the last third of itschord and closer to the trailing edge. The high incidence angle maycause separation and stall, but the addition of the propulsor at thesaid location will extend its operability well beyond the stall point.

In another embodiment, the injection of fluids such as water or liquidnitrogen to cool the hot gases delivered to the hot propulsor mayincrease the take-off thrust generated by said propulsor throughincrease in mass flow rate of the motive air. In case the propulsionsystem is embedded into an UAV, the amount of water on board of theaircraft may be such that after take-off, and end of the mission, whenthe fuel on board has been nearly consumed, the landing will not needthe additional thrust by at least 25% and up to 50%.

In yet another embodiment, the use of exhaust gas from the high pressureturbine as primary/motive fluid to the hot ejector may be augmented withadditional cold air compressor bleed, particularly to maintain a coldertemperature of the mix feed to the primary nozzles of the main hotpropulsor, particularly during level flight. In this manner, with themix at constant pressure and lowering of the temperature of the gasmixture, a longer life and/or cheaper materials may be utilized in theconduits. The modulation of the cold compressor air bleed may beperformed via a valve which switches the flow from supplying the coldpropulsor to the conduit feeding the hot propulsor, or via a secondaryinlet to the plenum of the hot propulsor to extend its life. In thiscase the cold propulsors become aligned with the main wing system or maybe retracted inside the fuselage and hence and do not participate tothrust generation.

The thermodynamic cycle of a typical jet engine is presented in FIG.30A. The evolution of the working fluid is described from end of theinlet (point 2) to 3 via a compression process, addition of fuel andcombustion at constant pressure via an isobaric process from 3-4,expansion over a turbine from 4-5. The latter provides the work requiredby the compressor and additional energy available for either driving afan (via a turbine connected to the fan) for a turbofan or directexpansion through a nozzle to atmosphere, in case of a turbojet. Thisembodiment of the present invention eliminates the free turbine requiredto drive the fan, connects the chopped fan to the main shaft of theengine and uses the energy of the combustion gases at point 45 toentrain and augment thrust via a specially designed ejector embeddedwith the aircraft, at all points during the mission of the aircraft(take off, transition, level flight, hovering and landing). Thethermodynamic evolution of the invented cycle takes the 45 gases via anearly isentropic expansion to a lower pressure at high efficiency, muchhigher than the expansion through a turbine. Process 45-A′ describes theevolution and can be recognized as nearly isentropic, as nozzleexpansions of this type are known to have very high efficiency. Theworking fluid evolution 45-A′ happens via a multitude of primary slotslocated within the ejectors described above. The expansion is continuedby a constant pressure or constant area mixing with approaching ambientair at p_(2static) conditions. The evolution follows A′-D′ for theworking fluid, while the ambient air is brought at constant pressurefrom inlet condition point C to D′. In this process of mixing atconstant pressure, the final temperature of the mixture depends on theentrainment ratio of ambient air into the ejector. As described below, aspecially designed ejector is utilized in this invention that maximizesthe entrainment ratio via several elements of said primary nozzles andmixing section of the ejector to values beyond 5:1 (five parts ofentrainment air per each part of primary working fluid). A pumpingeffect is next, elevating the temperature and pressure of the mixture ofhotter, primary fluid and entrained ambient air to T_(mix) and P_(mix)respectively, higher than the p_(amb). This is point D on the diagram ofFIG. 30B. A nearly isentropic diffusing and ejecting of the mixture isthe evolution D-E, with the final temperature and pressure of T_(exit)and P_(exit) respectively, where P_(exit) is equal to the ambientpressure at the aircraft speed. The point D location is in between point2 and point 5, closer to point 2 for higher entrainment ratios. Theadvantage of such as system is then obvious, noting that a large amountof air can be entrained and energized to produce thrust at lower mixturetemperature and velocity. This, in turn, allows the exhaust of suchthermodynamic cycle to be utilized not only for thrust generation but aswell for directing it advantageously over various airfoils foradditional lift generation, or vectoring it for VTOL and STOLcapabilities of the aircraft, at the exit of the cycle. In addition, theplacement of the entrainment inlet of the said ejectors in someembodiments may be such that boundary layer ingestion resulting from anairfoil such as a wing results, with additional benefits to the stallmargin of aid airfoil wing. In one embodiment, a first set of wingairfoils is such positioned that it operates at very high angle ofincidence, with very small margin to stall. By placing the said ejectorright behind the said airfoil apex point, in the area prone to developseparation of the boundary layer, the suction side (i.e. entrainmentside or inlet side of the ejector) determines that the stall margin isenhanced significantly, allowing a very high lift generation on saidairfoil/wing to be obtained, stall free.

Moreover, in some cases where a short take-off distance is desired,exhaust gas from a turbofan can be directed on the suction side of anairfoil (such as a flap). While several concepts have used thistechnique, there have been limited results. In this embodiment of thepresent invention, there is a higher lift proportional to the higherlocal velocity squared, at least for the portion of the wing exposed tothe thrust element emerging jets, because it utilizes the benefits ofdirecting the higher kinetic energy fluid (air of mixture of exhaustgas) directly to the pressure side of the wing or flap, instead of thesuction side, or directly to the leading edge much in the fashion of aturbo machinery airfoil (such as a turbine).

In addition, the exhaust of the ejector being at significantly lowertemperature and yet higher average exit velocity than the airspeed, maybe directed towards a secondary, downstream, thin airfoil as describedin FIG. 19D. In FIG. 19D, the ejectors 201 direct their efflux jetstowards the airfoils 202 which are thin and may be manufactured out ofreinforced composite materials. The higher efflux jet velocitydetermines a high lift force on the said airfoil compared to the liftgenerated by the said airfoil 202 would they only receive the airspeedflow of the aircraft. Conversely, the size and shape of the airfoils 202may be significantly reduced to produce a similar lift force as a verylarge wing. Reverting now to the inlet of the ejectors 201 and notingtheir placement right above the airfoil 203, the ingestion of theboundary layer developed past the apex of said airfoil 203 into theejector and this boundary layer being sucked in by said ejector 201determines a better stall margin of airfoil 203 and allowing it tooperate efficiently at higher angle of incidence.

In another embodiment shown in FIGS. 31A and 31B, the said cold ejectors801 are placed behind the airfoil 803 and in front of airfoils 802,still impacting both by increasing the stall margin on the 803 due tothe suction of the boundary layer of the said airfoil 803 and the liftforce due to higher speed of the efflux jet at 801's exit directedefficiently towards the airfoil 802. This allows a more aggressive levelflight position of both airfoils 803 and 802, shorter airfoils for samelift and swiveling of the ejector for vertical take-off, hovering andmaneuvering of the aircraft. It also allows more beneficial use of theefflux jet of the thermodynamic device to be used towards liftgeneration and not wasted to the environment, as it is the case forcurrent state of the art jet engines.

While this is not meant to be an exhaustive list, different embodimentsof the present invention are designed to provide for some or all of thefollowing improvements and advantages:

Enhance of the ability to maximize the thrust augmentation and vectoringof a jet efflux from a Coanda type flat ejector at all conditions offlight;

Enhance the efficiency and shorten the device for better integrationwith the wing or fuselage of the aircraft via introduction of particular3D features in the primary nozzle and Coanda surface;

Embed such a device with a wing to exploit the particular geometries ofthe wing in order to enhance the efficiency of the aircraft;

Enhance the primary nozzle efficiency to entrain secondary fluid and mixin the shortest period and length of the device via additional features;

Enhance the overall geometry in a non-circular fashion to allow itsefficient operation in level flight of the aircraft, in addition totake-off, hovering and landing while enhancing the propulsive efficiencyof the aircraft and eliminating the presence of nacelles and mainpropulsive engines on the wings and fuselage of the aircraft;

Generate additional thrust and lift due to a higher local velocity ofthe jet over the wing by using the residual kinetic energy of a jetefflux that usually only generates thrust via a mechanical connection;

Shorten the wings while preserving the same lift through extension ofthe diffusor walls of the propulsor as propulsion and lift generationdevice;

Improve the ejector to work at better at conditions away from idealconditions of a fixed geometry ejector (e.g., optimize operations andpropulsive thermodynamic cycles through the use of using 2 halves of anejector, being able to move them relative to each other and adding aflap-like feature to fully expand and collapse the ejector diffusorwalls);

Increase lift per wingspan ratio due to relatively low temperature ofthe jet efflux mixtures emerging from the propulsor and an axialvelocity component at higher values than the aircraft's velocity;

Include composites as a type of material used in thin airfoil due to itsability to withstand higher temperatures of the emerging mix jet efflux;

Reduce the overall dimensions and weight of the aircraft because theairfoil can be thinner in width and shorter in wingspan with a highmechanical resistance to stress;

Improve significantly the maneuverability and versatility of anaircraft, including allowing for V/STOL and hovering, via the swivelingand modulating the flow of both the propulsor and airfoil; and/or

Enhance the capabilities of aircraft attitude control, hovering and VTOLby allowing for a compact system with small swings and a distributedpropulsion system, particularly in UAV, UAS and drones.

Furthermore, in addition to the many features mentioned above, differentembodiments of the present invention may also have some or all of thefollowing improvements and advantages:

The thermodynamic cycle is simpler, with an ejector/eductor type elementreplacing the entire fan and low pressure turbine subsystemfunctionality hence reducing the weight of the system by at least 30%.This is particularly advantageous for smaller UAV type systems where theturbofans are not efficient due to reasons explained above;

The potential to swivel or vector the eductor type propulsorsindependently and to allow for take off and land vertically, withoutmoving large rotating parts;

The potential to modulate the flow to these propulsors during take-offand level flight as well as at landing and emergencies thereforeapplying different thrust levels at various locations of the aircraft,and to completely isolate any number of the said propulsors;

The potential to eliminate large rotating part components withnon-moving parts of same functionality, i.e. fan replaced by fluidicpropulsor/eductor; a direct improvement in life of components isexpected from non-moving vs. rotating parts, especially for small UAVsand airplanes where the dimensions of the fan require very high speeds;

The potential to use light and high temperature materials such ascomposite materials, carbon fiber based materials and CMCs for theconduits and propulsors;

The potential to modulate the bleeds such that at level flight only thehot propulsors are supplied with hot gas or a mixture of hot exhaust gasand colder, compressor air bleeds from the gas generator;

The benefit that the gas generator is operated at optionallyadvantageously same rotational speed without large excursions in RPMsbetween take off and cruise, far away from the surge or stall line;

The benefit of giving any shape to the propulsor and able to integrategreatly with the fuselage and wings of the aircraft;

The benefit of having large entrainment and turbulent mixing inside saidpropulsors such that the jet efflux from their exhaust is low enough intemperature to allow an airfoil for lift or attitude control of theaircraft to survive and function properly including generating more liftusing the higher velocity jet; and/or

The benefit of embedding the propulsor into the wing behind the wing'scamber apex whereabouts the boundary layer would otherwise separate athigh angles of incidence, thereby ingesting said boundary layer anddelaying its separation and increasing the tall margin of the said wingat level flight.

It should be noted that any of ejectors 701, 801, 901 can be configuredusing any ejector geometry described herein.

Although the foregoing text sets forth a detailed description ofnumerous different embodiments, it should be understood that the scopeof protection is defined by the words of the claims to follow. Thedetailed description is to be construed as exemplary only and does notdescribe every possible embodiment because describing every possibleembodiment would be impractical, if not impossible. Numerous alternativeembodiments could be implemented, using either current technology ortechnology developed after the filing date of this patent, which wouldstill fall within the scope of the claims.

Thus, many modifications and variations may be made in the techniquesand structures described and illustrated herein without departing fromthe spirit and scope of the present claims. Accordingly, it should beunderstood that the methods and apparatus described herein areillustrative only and are not limiting upon the scope of the claims.

What is claimed is:
 1. A vehicle, comprising: a main body having a foreportion, a tail portion, a starboard side and a port side; a gasgenerator coupled to the main body and producing a gas stream; at leastone fore conduit fluidly coupled to the generator; at least one tailconduit fluidly coupled to the generator; first and second fore ejectorsfluidly coupled to the at least one fore conduit, coupled to the foreportion and respectively coupled to the starboard side and port side,the fore ejectors respectively comprising an outlet structure out ofwhich gas from the at least one fore conduit flows at a predeterminedadjustable velocity; at least one tail ejector fluidly coupled to the atleast one tail conduit and coupled to the tail portion, the at least onetail ejector comprising an outlet structure out of which gas from the atleast one tail conduit flows at a predetermined adjustable velocity;first and second primary airfoil elements having leading edges, theprimary airfoil elements respectively coupled to the starboard side andport side, the leading edges of the first and second primary airfoilelements being respectively located directly downstream of the first andsecond fore ejectors such that the gas from the fore ejectors flows overthe leading edges of the primary airfoil elements; and at least onesecondary airfoil element having a leading edge and coupled to the mainbody, the leading edge of the at least one secondary airfoil elementlocated directly downstream of the outlet structure of the at least onetail ejector such that the gas from the at least one tail ejector flowsover the leading edge of the at least one secondary airfoil, wherein:the gas generator comprises a first region in which the gas stream is ata first temperature and a second region in which the gas stream is at asecond temperature, the second temperature higher than the firsttemperature; the at least one fore conduit provides gas from the firstregion to the first and second fore ejectors; and the at least one tailconduit provides gas from the second region to the at least one tailejector.
 2. The vehicle of claim 1, further comprising first and secondcanard wings coupled to the fore portion and respectively coupled to thestarboard side and port side, the canard wings configured to developboundary layers of ambient air flowing over the canard wings when thevehicle is in motion, the canard wings being respectively locateddirectly upstream of the first and second fore ejectors such that thefirst and second fore ejectors are fluidly coupled to the boundarylayers.
 3. The vehicle of claim 2, wherein the first and second foreejectors respectively comprise first and second inlet portions, and thefirst and second fore ejectors are positioned such that the boundarylayers are ingested by the inlet portions.
 4. The vehicle of claim 1,wherein the gas generator is disposed in the main body.
 5. The vehicleof claim 1, wherein the gas stream produced by the generator is the solemeans of propulsion of the vehicle.
 6. The vehicle of claim 1, whereinthe first and second fore ejectors each have a leading edge, and theentirety of each of the first and second fore ejectors is rotatableabout an axis oriented parallel to the leading edge.
 7. The vehicle ofclaim 1, wherein the first and second fore ejectors each have a leadingedge, and the entirety of each of the first and second fore ejectors isrotatable about an axis oriented perpendicular to the leading edge. 8.The vehicle of claim 1, wherein the at least one tail ejector has aleading edge, and the entirety of the at least one tail ejector isrotatable about an axis oriented parallel to the leading edge.
 9. Thevehicle of claim 1, wherein the at least one tail ejector has a leadingedge, and the entirety of the at least one tail ejector is rotatableabout an axis oriented perpendicular to the leading edge.
 10. Thevehicle of claim 1, wherein at least one of the outlet structures isnon-circular.
 11. The vehicle of claim 1, further comprising a cockpitportion configured to enable manned operation of the vehicle.